iPhone 8 doesn't appear in finder anymore!?

Have you tried rebooting the computer? I'd even try rebooting the iPhone as well.

Try disconnecting all other external devices from the computer and connect the iPhone directly to the computer.

Have you tried booting into Safe Mode and connecting the iPhone?

Have you tried rotating the USB-C connector 180º upside down?

Try using the USB-C ports on the other side of the laptop.

"iPhone 8 doesn't appear in finder anymore!?: [...]I tried with a newer MBP of a friend of mine and immediately the iPhone was in his finder with the same cable that I used with MBP.[...]"

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iPhone Not Being Seen in Finder:

A. Verify the Connection:

First off, see if the headphones are is even seen: 

1. Hold Down: the Option key
2. Click: the Apple menu
3. Choose: System Information or System Report
4. Select:  USB from the list on the left
5. Look For: the iPhone

B. Reset the SMC and your NVRAM:

(Applies to Intel-Based Macs only): Sometimes when changes are made to the system(i.e. updates), system configurations (i.e. for USB Ports) become manipulated, technically. So, reset the SMC and NVRAM, if applicable.

See if anything in this link helps --> If your computer doesn't recognize your iPhone or iPad - Apple Support

Check Finder > Settings… (it might be called Finder > Preferences… in Monterey) to make sure that you have checked off the box that will cause the Finder to show your iPhone in Finder window sidebars.

Hi,

Welcome to Apple support community!

Please try sign out and and sign in again to the Apple ID on your device. Even I had faced the issue and this helped me to fix it. :)

Thanks,

Sajith

“headphones working fine: in sys profile-usb i don't see the iPhone i did both (smc and pram) but nothing happened”

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Copy & Paste Error:

First off, see if the iPhone is even seen.

SMC & NVRAM Reset:

Perform the resets thrice —3 resets for each. It can will take some time to perform a total of 6 resets. So, be certain you have the time to do so.