Port Replicator VGP-PRS35

The 500 GB disk drive in my Port Replicator VGP-PRS35 just stopped working.  Does not appear in File Manager, Disk Management and no drivers appear to be missing.  How do I determine if this is a software or hardware issue to fix?  It has been working with no problem for over two years.

I am running Windows 10 on a SVS1512DCXB C60BTZAB.