Thanks for the reply. The error is
"Access to fetch at 'https://realmcraft-400614.nw.r.appspot.com/' from origin 'https://html-classic.itch.zone' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled."
Bit weird because thats in the allow list...
EDIT: Turns out the problem was actually that billing had failed for all my cloud services, and this was showing up as a CORS issue. So it wasn't a CORS problem after all! 🫠 Thanks anyway 🫶