Sadly, it seems it has shuffled off this mortal coil. They do that sometimes. Not much you can do other than buy a new drive and reinstall...

There are people who can retrieve data from deceased drives, but it tends to be prohibitively expensive due to the time it can take and the actual fault on the drive. I'll not bore you with unnecessary detail...!

You may just get lucky and the drive leaps back into action after being left for a while - if it does, use the time to migrate it to a new drive because it won't be reliable.