What are the reasons why Ubuntu can’t mount a USB drive?

1. The USB drive itself may be faulty due to hardware issues such as poor connection or damaged chips, resulting in failure to be recognized and mounted by the system.
2. The file system format is not supported: If the file system format of the USB drive is not supported by Ubuntu, such as exFAT, the system may not be able to properly recognize and mount the USB drive.
3. The mount point is already in use: It is possible that another device or file system has already occupied the mount point, preventing the USB flash drive from being mounted.
4. No permission: the current user may not have enough privileges to mount the USB drive, permission settings need to be adjusted accordingly.
5. System configuration issue: The system may have some configuration problems, such as missing drivers or software packages, which may prevent recognition and mounting of the USB drive.

Solution: You can try manually mounting the USB drive using the command line, checking the file system format of the USB drive, ensuring the mount point is not occupied, verifying the user permissions, and also attempting to unplug and reconnect the USB drive or trying to mount it on a different system. If the issue persists, it may be necessary to further investigate and repair any system configuration problems.