Well, there could be various reasons for hard drive to become unresponsive or undetected. It can be a hardware issue or some technical glitch in the software.
Below are the few possible reasons for any drive being unresponsive:
1. Lot of bad sectors
2. Infected File (Virus or Malware)
3. Driver issue
4. Mechanical failure
You can try the below options to resolve the issue:
1. Run CHKDSK
2. Use an Antivirus & Anti-Malware tool
3. Re-install the drivers
Hope this will help.