Just in case this sheds any light on the issue ...
I'm on CC, but a friend required some help with a Premier Elements project. As this appears not to be available through the cloud, I installed it from my (legal) disks.
After working with Premier for a bit, I went back to my PS work, and encountered the problem described above.
Uninstalled Premier Elements.
reopened ps and was prompted to enter my account details
Now everything works as expected.
