Hello there, based on your description that your flash drive no longer appears on your Mac desktop after the OS update, which previously worked fine, I believe there is something wrong with your OS. You're recommended to reset the SMC on your computer.
Here is how to reset SMC on Mac with a T2 chip:
1. Shut down your Mac.
2. Press and hold the power button(or Touch ID button) for 10 seconds until the Mac shuts off, then restart it.
3. If that doesn't fix the problem, turn the Mac off again.
4. Press and hold the right Shift key, the left Option key, and the left Control key for 7 seconds.
5. Keep holding all these three keys and hold the Power button for another 7 seconds.
6. Release all the keys and wait a few seconds. Now restart your MacBook.
Here is how to reset SMC on Mac without the T2 chip:
1. Shut down and unplug your Mac.
2. On the built-in keyboard, press and hold the Shift, Option, and Control keys on the left side and press the Power button and hold all of these down for 10 seconds.
3. Release all four keys.
4. Connect the power adapter and then turn the Mac on.
Jessica Shee
Ciki Liu
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