Here is the error from dmesg I’ve got when trying to mount external HDD:
Trying to mount as ext2 didn’t change anything:
fsck didn’t want to help and was stopping after this:
What you can try to do to recover at least some data is to use backup superblock. Run mke2fs command (as root):
Notice the numbers at the end, let’s try fsck with one of the superblock backups:
It did work for me, good luck and let me know how did you do!