Timboli: the timeout, if that was the issue, happened real soon, very much sooner than it should have, which made it feel like it wasn't even trying.
That sounds like it could be a completely different issue than what I saw. I think I always got the spinner and I think the internal timeout is 15 seconds. It still takes over half that now that it works so it still spins for a while.
Edit: Oops, reading your message again I see is working for you now, but for anyone who isn't seeing it working and not seeing a timeout maybe the following would be helpful (reworded a bit).
I can think of three possible issues:
1) Browser compatability issue? I'm using Firefox on Linux with a number of changes and addons but I tried it in a fresh profile and it still works so if you haven't tried with Firefox (without addons, go to about:profiles and make a new profile or at least restart without addons) I would try that first.
2) Cache issue? I don't know enough about javascript to know how the cache is supposed to work but it seems like caching for more than just while the page is open would cause quite a bit of trouble so I doubt this is it unless you have a separate caching layer that is ignoring that the remote request should not be cached. Trying a search you haven't tried before would be one way to check this.
3) Something you did got you on an automated list and GOG doesn't let you use some more performance sensitive things (maybe just during major sales?). I think these types of lists tend to auto remove you after 1-3 months unless you trigger it again meanwhile.
To check the network request: in Firefox right click anywhere on the page and click inspect, then go to the Network tab. Don't reload the page but just enter a search term that you haven't used before. There should be a request where the file starts with data?canceled= so look for the status of that request. I guess an error status here could be either the timeout or #3 above while not seeing a request (or if it doesn't have a search= part with your search term) would be #1 or #2. Likely there are other possibilities too.