Fedia Discussions

Apologies if I'm asking an easy to answer question. I seem to be having some issues with federation from other sites, particularly sopuli.xyz.

https://fedia.io/m/linux@sopuli.xyz works fine
https://fedia.io/m/fountainpens@sopuli.xyz gives a 404, but !fountainpens@sopuli.xyz is viewable directly on that site and federated at beehaw.org (beehaw.org/c/fountainpens@sopuli.xyz).

I have no idea why this is happening. Can individual communities/magazines defederate from particular sites? If not, why would I get such different results from two communities on the same server?

Thanks,