Problem using Elements 15

I've been using Photoshop (Adobe Elements 15) for years and recently got a new desktop to replace my old one.  When I try to use Photoshop I get an error that says too many devices are using this serial number.  I go into my Adobe account and it says I don't have any activated devices (so I can't deactivate one)!  The program won't start and I don't know what else to try.  I have already tried downloading it again, but I get the same error msg.