iPhone 12 disappears from Big Sur Finder

Alternate ways to Fix these issues are kill the USB process through the Command line, Keep your iPhone connected to Mac and open the terminal from the launchpad, or Using Spotlight search. Type this command in a terminal or copied into the terminal.

sudo killall -STOP -c usbd

Click on the Return button to run the command and Enter your Mac password to execute the process.

Once the process is killed, Your iPhone will see on the Finder sidebar.

Hello SCADA-Guy,

Thank you for reaching out to Apple Support Communities. We are happy to help you!

We understand that you are having trouble with syncing/playing music on your new device. It seems that you are able to connect the phone to your MacBook for a short period of time, but then the "trust" pop up window disappears. Are you using an official apple cord for the connection? Or a third party cord? We want to make sure that being that this issue has persisted, to make sure you are using an official apple cord.

Nonetheless, we have provided you with some helpful information to assist:

Turn on Sync Library with Apple Music

"Turn on Sync Library

With the latest version of iOS, iPadOS, and macOS, Sync Library is turned on by default. If you turned off Sync Library, you can turn it back on. Just follow the steps below for your device.

On your iPhone, iPad, or iPod touch

1. Go to Settings > Music.
2. Turn on Sync Library. If you don't subscribe to Apple Music or iTunes Match, you won’t see an option to turn on Sync Library.

If Sync Library is updating or turned off, you'll see a message at the top of the Library tab in the Apple Music app."

If songs are missing from your music library after you turn on Sync Library

If your computer doesn't recognize your iPhone, iPad, or iPod

"If your computer doesn't recognize your connected device, you might see an unknown error or a "0xE" error. Follow these steps and try to connect your device again after each step.

1. Make sure that your iOS or iPadOS device is turned on, unlocked, and on the Home screen.
2. Check that you have the latest software on your Mac or Windows PC. If you're using iTunes, make sure you have the latest version.
3. If you see a Trust this Computer alert, unlock your device and tap Trust. If you can't unlock your device because you forgot your passcode, find out what to do.
4. Unplug all USB accessories from your computer except for your device. Try each USB port to see if one works. Then try a different Apple USB cable.*
5. Restart your computer. 
6. Restart your iPhone, iPad, or iPod touch.
7. Follow these additional steps for your Mac or Windows PC. 
8. Try connecting your device to another computer. If you have the same issue on another computer, contact Apple Support."

Connect iPhone and your computer with a cable

We hope this finds you well!

Cheers!

Hello SCADA-Guy,

It seems that the main issue is a connection between your iPhone and Mac computer.

We would suggest to Contact Apple Support for further assistance.

We hope this finds you well!

Cheers!

I have the same problem. In the finder, it shows my iPhone for a second and then disappears indefinitely. It shows other devices without any problems, usb stick, external hard drive