Device activation limit warning - but I only use one device

From time to time I am prompted to enter my Adobe ID/password when I launch PS or LR. And then I get thie message below.

The two boxes with the green tick are both the current PC, so I assume this is locked/crashed sessions - but PS and LR have not locked up for many months now. They're very stable.

Whenever I see this dialog I always click on Sign Out on both boxes. In fact I must do this because I cannot proceed if I dont.

Then strangly, the message will appear later - it could be a few days, or a few weeks, there is no pattern and the times listed in the boxes could be the same or completely different.

Any clues?

I dont think it is PS or LR locking up. Maybe CC itself?

Windows 10 on an AMD PC. I have power settings to put the PC in sleep mode when unused. This can happen with LR or PS open so this may be related to the problem.