What's your detailed problem?
Did you receive a "not formatted error" message? Was your drive displayed as RAW or corrupted? Or was it not detected by the computer?
If your problem is one of the former three, you could try a hard drive recovery freeware to get back you data and format this drive to save it afterwards. Honestly, this freeware has helped my friend recover his inaccessible data from a RAW drive. You could try it to take a chance. Note:
1. Stop writing anything new on your computer to avoid 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. Format this drive to see whether it could work as before.
4. Back up your data regularly in the future.