Summary: Don't know how to fix when USB flash drive is not mounting on Mac? Try these 4 solutions in this page and use iBoysoft Data Recovery for Mac to recover lost data necessarily.

1. Back up your data on the Mac where you want to install Catalina. Here, insert the plug-in into the USB flash drive and click 'Create a bootable installer'. After creating the drive, plug it into an unsupported Mac and install macOS Catalina in it. Turn on your Mac and hold down the Option key.
2. However, if the USB flash drive is not mounted on Mac, you will lose access to the USB flash drive as well as to the data stored on it. But don't worry, this page talks about the reasons for this issue, and how to fix 'USB flash drive not mounting on Mac' without data loss even if external hard drive is not showing up on Mac.
3. Apple hasn’t shipped operating systems on physical media in a full decade, but there are still good reasons to want a reliable old USB stick for macOS Catalina.Luckily, it's not hard to make one.

Adobe Flash Player for Mac is the standard for delivering high-impact, rich Web content. Designs, animation, and application user interfaces are deployed immediately across all web browsers and platforms, attracting and engaging users with rich Web experience. Adobe Flash Player for macOS supports several data formats including AMF, SWF, XML and JSON. The multimedia formats which.

When I plugged in my USB flash drive on macOS High Sierra, I can't see it in Finder or on the Desktop. So, I went to Disk Utility, it was there. But the USB flash drive was grayed out in Disk Utility and I could not mount it. How can I fix/repair USB flash drive not mounting issue on Mac?

It is user-friendly that Mac will automatically mount the inserted USB flash drives. However, if the USB flash drive is not mounted on Mac, you will lose access to the USB flash drive as well as to the data stored on it. But don't worry, this page talks about the reasons for this issue, and how to fix 'USB flash drive not mounting on Mac' without data loss even if external hard drive is not showing up on Mac.

Why the USB flash drive is not mounting on Mac?

What makes USB flash drive unmounted on Mac can be various, in that this external drive is connected to the Mac computer through USB cable, USB port. The possible reasons for this issue include:

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• Faulty connections like broken cable and wobbly USB port
• File system errors, volume header corruptions, etc. in the USB flash drive
• Disk Utility failure, log file corruption, OS malfunction on this Mac
• Physical damage and other factors

How to fix/repair USB flash drive not mounting issue on Mac?

No matter what results in unmountable USB flash drive, it's urgent to fix/repair USB flash drive not mounting issue on Mac. Here are 4 solutions to this unmounted USB flash drive issue according to different causes, you can check them one by one.

Solution 1: Check the USB flash drive in System Information

If you plug this USB flash drive into your Mac computer but get no sign that this drive is mounting on Mac, you can check System Information to see if this USB flash drive is showing up.

1. Step 1: Go to Utilities and choose System Information.
2. Step 2: Double-click on its icon to open it and choose USB in the left sidebar.
3. Step 3: Check if your USB flash drive is detected by the system in the right box.

If your USB flash drive is not showing up in the right box, you can try to re-plug it, or change another USB port and cable to connect it.

Solution 2: Check the Finder Preferences

Sometimes, you just can't find the USB flash drive in Finder and on the desktop, but actually, it is mounted on your Mac and just not showing up. Check the Finder Preferences and see if it will appear.

1. Step 1: Click Finder and choose Preferences in the top menu bar.
2. Step 2: Check External Disks in General tab so that the USB flash drive can be shown on the desktop.
3. Step 3: Go to Sidebar and check External disks so that they can be located in Finder.

Solution 3: Check and repair this USB flash drive with Disk Utility

If you still can't access your USB flash drive thereafter, you can go to Disk Utility which is a built-in utility to fix disk problems. If it is greyed out in Disk Utility, you can manually mount this USB flash drive.

1. Step 1: Go > Utilities > Disk Utility.
2. Step 2: Click on View option and choose 'Show all devices'.
3. Step 3: Click on the name of your USB flash drive.
4. Step 4: Select Mount in the upper menu bar.

If the Mount button is greyed out and you can't mount this USB flash drive manually, then there could be some disk errors. Fortunately, you can use First Aid in Disk Utility to repair this unmountable USB flash drive.

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1. Step 1: Launch Disk Utility.
2. Step 2: Choose the grayed-out USB flash drive.
3. Step 3: Select First Aid in the top center and click Run.

Solution 4: Fix the unmountable USB flash drive by reformatting

However, if Disk Utility fails to repair this external drive because of serious file system corruption, you can only fix this by reformatting. The thing you need to keep in mind is that reformatting will erase all files on this USB flash drive, which means, you need to make sure an existing file backup. Or you can recover lost data from the unmountable USB flash drive before you fix the USB flash drive not mounting issue on Mac by reformatting.

How to recover lost data from unmounted/unrecognizable USB flash drives?

Can't open the unmountable USB flash drive but don't want to lose data? You can still get your files back with USB flash drive data recovery software before you reformat this drive.

As one of the most professional USB data recovery software, iBoysoft Data Recovery for Mac is highly recommended. It can recover lost data from unmountable, unreadable, and corrupted USB flash drive, recover deleted/lost files from emptied Mac trash. Moreover, this software performs well in recovering data from hard drives, external hard drives, flash drives, USB sticks, SD cards, and other storage devices. Data recovery is allowed on macOS 10.14/10.13/10.12 and Mac OS X 10.11/10.10/10.9/10.8/10.7.

Step 1: Recover lost data from unmountable USB flash drive with Mac data recovery software

1. Step 1: Download and install iBoysoft Data Recovery for Mac on your Mac.
2. Step 2: Connect your USB flash drive to the Mac and launch iBoysoft Data Recovery for Mac.
3. Step 3: Select the unmountable USB flash drive and click 'Next' button to scan all lost files.
4. Step 4: Preview the scanning results by double-clicking, choose files that you want to recover, and click 'Recover' button to get lost data back.

Note: In case you lose the recovered files again in the next reformatting step, you'd better save these files to another reliable drive.

Step 2: Reformatting this USB flash drive without data loss

After recovering data from this unmountable USB flash drive, you can reformat this USB flash drive without worrying about losing anything important.

1. Step 1: Go > Utilities > Disk Utility.
2. Step 2: Click the icon of unmountable USB flash drive on the left part of the window.
3. Step 3: Click the Erase button on the top of the Disk Utility window.
4. Step 4: Complete the related information(name, format, scheme), then click Erase button.

When the process finished successfully, your USB flash drive will be mountable on the Mac computer again. But the case is, no matter how powerful USB flash drive data recovery software is, the best way to recover files from external drives is to recover them from backups. So, remember to duplicate your files this time.

Catalina Mac Update

You may also want to know:

HSD not mounting or seen in Disk Utility? Tutorial to fix SD card not mounting on Mac and recover lost data from unmountable SD card on macOS.

These instructions are NOT applicable to Flash Player included with Google Chrome. Visit the Flash Player Help page for instructions on enabling (or disabling) Flash Player in various browsers.

If you use Windows, see Uninstall Flash Player | Windows.

Mac Catalina Issues

If Flash Player is installed on your computer, the following box displays the version of Flash Player and your operating system. If Flash Player is not installed, an error message appears.

If your Flash Player installation was not successful, use the following solution to reinstall.

Click the Apple icon and choose About This Mac.

The Mac OS version appears in the About This Mac dialog.

• Run the uninstaller on Mac OS X 10.4 and later, including macOS
  

Note:

Beginning with Flash Player 11.5, uninstalling the Flash Player resets the AutoUpdateDisable and SilentAutoUpdateEnable settings in mms.cfg to their default values:

• AutoUpdateDisable=0
• SilentAutoUpdateEnable=0

If you are running the Flash Player uninstaller as part of your deployment process, redeploy any custom changes to either AutoUpdateDisable or SilentAutoUpdateEnable.

Download the Adobe Flash Player uninstaller:

• Mac OS X, version 10.6 and later: uninstall_flash_player_osx.dmg
• Mac OS X, version 10.4 and 10.5: uninstall_flash_player_osx.dmg

The uninstaller is downloaded to the Downloads folder of your browser by default.

In Safari, choose Window > Downloads.

If you are using Mac OS X 10.7 (Lion), click the Downloads icon displayed on the browser.

To open the uninstaller, double-click it in the Downloads window.

Note: If the Flash Player installer window does not appear, choose Go > Desktop in the Finder. Scroll down to the Devices section and click Uninstall Flash Player.

To run the uninstaller, double-click the Uninstaller icon in the window. If you see a message asking if you want to open the uninstaller file, click Open.

Bookmark or print this page so that you can use the rest of these instructions after you close your browser.

To close all browsers, either click the browser name in the Uninstaller dialog, or close each browser manually and then click Retry.

Note: Do not click Quit in the Uninstaller window. It stops the uninstallation process.

After you close the browsers, the uninstaller continues automatically until the uninstallation is complete. When you see the message notifying you that the uninstallation succeeded, click Done.


Delete the following directories:

• <home directory>/Library/Preferences/Macromedia/Flash Player
• <home directory>/Library/Caches/Adobe/Flash Player

Download the Adobe Flash Player uninstaller:

• Mac OS X, version 10.3 and earlier: uninstall_flash_player_osx_10.2.dmg (1.3 MB) (updated 05/27/08)

Choose Window > Downloads to view the downloaded uninstaller.

Save the uninstaller file in a convenient location.

To open the uninstaller, double-click it in the Downloads window.


To run the uninstaller, double-click the Uninstaller icon in the window. If requested, enter your computer user name and password and click OK.

Bookmark or print this page so that you can use the rest of these instructions after you close your browser. Close all browsers and other applications that use Flash Player, including instant messaging applications, SWF files, and projectors (EXE files that play SWF files). Otherwise, the uninstaller cannot finish (even though it appears to finish).

Once the uninstaller finishes, the window closes automatically.

You can verify that uninstallation is complete by following these steps:

Open your browser and check the status of Flash Player.