Disappearing e-books

I opened ADE on my PC tonight and discovered that all my books had disappeared! I rebooted 3 times, then reinstalled the software. Any suggestions to get them back?

I also checked the sync setting on my new Moto G Stylus phone. No books there, either, not even the sample books that I downloaded tonight on the PC.

Suggestions? Or is time to move to Kindle & their Tech Support?