Adobe thinks my registered copy of CS6 is a "free trial".

There are ways to activate CS6; you can search here for prior discussions or wait for someone with that info to see your post.

But what you've done is validate my comments: yes, it's worked great... until now. But there's no support for versions that old, technical or CS. I think Adobe has formally closed out some older versions, meaning their entire response is "Good luck!" This issue is not going to go away, and next year you may not be able to reactivate it again when your system hiccups. Only part of this is in Adobe's hands; older OSes and older hardware have all their own age-out issues as well. Computers don't simply keep working forever unless they are wholly standalone.

(ETA: I'm not sure it's reasonable to expect live support on a product that old, to be honest, but for some reason software is thought to be eternal in that respect.)

I understand all the arguments and issues — and the resistance to the subscription model — but you and your clients are hanging out on a wire, here. I'd start looking for more stable solutions; you might look at Affinity Publisher, for example, which is a semi-compatible tool of modest cost that is not subscription-based. (Which then brings back all the fun of the bad old days of no two shops having compatible versions of the software, but you can't have everything.)