Why isn't Windows 11 recognizing my exFAT disk?

First, check how the disk appears in Windows Disk Management. Is the disk listed, and does its partition show as exFAT with a drive letter? A partition without a letter may just need one assigned. If the disk or partition is missing entirely, that points to a different problem than File Explorer not showing it.

Don't initialize, delete, or format anything there while you're trying to keep the backup. Those actions can make recovery harder.

On Linux, use lsblk -f and sudo fdisk -l to check that the exFAT filesystem is on the partition you expect and that the GPT layout looks normal. Unmount the partition before running sudo fsck.exfat -n on it. The -n option checks without making repairs.

Double-check the device name before running any disk command. If the check reports errors, keep another copy of the files before attempting a repair.

If Windows detects the disk but still can't read the partition, formatting it as exFAT in Windows is another thing to try. That erases the partition, so copy the files somewhere else first. Then check that both systems can read it before putting the backup back.

A partitioned exFAT disk isn't automatically the problem here. This is a SATA disk, not necessarily removable media, so I wouldn't wipe the partition table just because Windows doesn't recognize it.