It seems that your drive get the “not formatted” problem. It is really common. Format is always the efficient solution of your problem.
But, if you want to recover your files inside this drive, you should try
a free hard drive recovery tool, which has successfully recovered my inaccessible data from a “not formatted” drive. You should try it, too.
Note:
1. Stop writing anything new on this drive immediately to avoid the original data overwritten by new data , which can make your data gone permanently.
2. Save your recovered data on a different drive in case of recovery failure.
3. Not forget to format this drive to see whether it could work as before.
4. Back up your data in a safe place.