I just saw a forum thread from 2014 talking about Fences asking for activation code out of the blue. Here we are, nearly 5 years later, and the problem still exists!!!
ONe wasy this can happen if you have run into max activations and were prompted to deactivate all PCs. The other, still active PCs, would request reactivation. If you are perpetually over the limit (5), the cycle will continue.
The other way is if you change your PC hardware enough that the PC looks different to us - it looks a like a new PC. It will then wasnt to reactivate.
The first does not appear to be the case for you.
Should it happen again, just follow this process:
https://forums.stardock.com/486311/accounts-and-activation-support-faq#error212
Sean Drohan
Stardock Support Manager