George replied to my email. He stated that he figured out the issue and patched the server. He'll probably comment here soon.

 I just sent an e-mail to support@kronosaur.com and pointed him at this thread, so he should know soon if he doesn’t already. If worse comes to worst, I’ll poke him about it tomorrow during his weekly stream. Don’t panic, I’ll make sure he gets the word. Thanks! I emailed earlier too with the debug...

I am also having this error. Delay when logging in and I can't access any expansions. Same RPC error as above.

EDIT: Tried 18.3 too, same thing. Tried clearing Cache, checking firewall too.