I've lost count of how many times this problem has come up, not just here, but from many friends and neighbors. All storage systems, be they hard disks, SSD, CD, DVD, etc., will fail at some point. In the case of the hard drive, it's a mechanical device that spins at thousands of revolutions each second. This creates wear, and at some point the positioning may be off a fraction of a millimeter and it can no longer read the contents. It's also possible that a critical part of the drive, for example the directory, has a section that is no longer readable. In the majority of cases, recovery is not possible. There are services that will attempt heroic efforts like disassembling the drive in a dust-free chamber so that it can be combined with parts from a working drive to recover the data. This is horrendously expensive, and not guaranteed to work.

In the past I have had exactly one time where data could be recovered without expense. A neighbor delivered newspapers every day, and had her entire route and records on an external drive. It failed. She called me in desperation, because there was no backup. After a few failures I tried standing the drive on edge, on the theory that gravity might pull the spinning shaft back into a position of less wear. It worked, and the data was recovered. So try placing the drive in different positions. If you've live a good life and accrued enough Karma points, it might work. I would caution about spending a large amount of money on data recovery, as the odds are against you.

It's probably worthwhile to repeat the 3-2-1 backup rule, which has served me well:
3 - Have at least 3 copies of your critical data
2 - Keep those copies on at least 2 different types of media
1 - Have one copy that is in a remote (i.e. not in your home) location

My favorite offsite backup service has a slightly different take on this: https://www.backblaze.com/blog/the-3-2-1-backup-strategy/