User blog comment:Harrypotterexpert101/Potential Adoption: Community Discussion!/@comment-26339491-20190617183601/@comment-26339491-20190618173742

Discussions and the wiki use the same login, but most Discussions users are on the Fandom app or the old Hunger Games community app. If you're logged in there, you can post in Discussions, but you can't edit pages, and may have trouble opening pages that aren't in the main namespace of the wiki.

If you then go to your browser app to visit Fandom, your login from the app isn't carried over, since they're two separate apps. I hope that makes sense!