Guys, after I shut down my laptop with the External SSD with exFat (2 Tb) plugged in, when I finished doing a backup via grsync I couldn't mount this device anymore. He tells me he couldn't ride. Then I ran the command:

walnut@Nitro5:~$ sudo exfatfsck -a /dev/sdd1
[sudo] password for walnut:
exfatfsck 1.3.0
Checking file system on /dev/sdd1.
ERROR: invalid cluster 0x10400200 in clusters bitmap.
File system checking stopped. ERRORS FOUND: 1, FIXED: 0.

So I don't know how to fix this. What amazes me is that in Windows 7 on a friend of mine's laptop it mounts and reads what's inside.
I'm using updated Linux Mint 20.3.
Ah, I also booted the Laptop with Ubuntu from another External HD (which is not SSD) and it managed to mount the External HD with the SSD.
It looks like the error is with Linux Mint installed on my laptop. Is it a problem in /etc/fstab or in another file that manages the mounts?
What do you suggest as an attempt to solve this? Should I reinstall Linux Mint 20.3 or another Linux distribution?
Thanks in advance for any help.

According to google, exfatfsck can't repair errors "exfatfsck checks an exFAT file system for errors. Note that it cannot repair corrupted FS, it just reports found errors." (From the man page)

The best way to fix is to plug it into a Windows system and scan and fix errors there. The following page has instructions for various Windows versions: https://neosmart.net/wiki/chkdsk/

Can't imagine why that would amaze anyone as exfat is a Microsoft windows filesystem and one would certainly expect it to work better on any windows system. Many Linux systems do not have software installed to work with exfat by default as it was designed for specific uses and is not used as much as vfat or ntfs. You might have these utilities on your Ubuntu and not installed on Mint so go to the site below which explains how to install them.

https://linuxize.com/post/how-to-mou...ive-on-ubuntu/