WD Blue 500GB Unable to See Files

I am trying to use a WD Blue 500GB, WD5000LPVX bare drive as a backup drive on my Dell 15, Inspiron 5558 laptop. I am using a Sabrent adapter to connect the drive to an external USB port. The drive shows up as “USB DRIVE”, with a drive letter but when I try to open the drive, a message appears “Please Insert a Disk into USB Drive.” When I examine the drive properties, it shows that the driver is installed and the drive is working. I can hear the disk turning with no unusual noise. The drive worked as the internal system drive when I replaced it with an SSD. Any suggestions what might be the problem.
Thanks, Craig