I would create a live media if you don’t already have one. Boot into that, try to mount your partition and chroot into it. Run

lsblk -f

Look for the UUID of the partition and copy it. Edit /etc/fstab and swap the UUID of the partition with the one you just copied.

Try that. Not a definite fix, but that would be the first thing I try, from memory.

EDIT: this assumes it is your main partition that is not being found, otherwise, you should be able to access /etc/fstab without a live media.