I can't figure out how to get rid of this "language_not_allowed" problem.

I have this issue with all of the apps I'm trying out—Memmy, Mlem, and wefwef—so obviously this is a "me" issue or a "lemmy" issue. I can't figure out how to set my language in Lemmy though. I've set my profile languages to "Undetermined" and "English" and I've turned on all languages on my server.

However, when I post directly from my server's primary interface, I do always need to manually select the language.

Does anyone have any idea to what I'm doing wrong? I'd love to get this fixed, and hopefully it'll help anyone else having a similar problem. If there's just a doc somewhere I missed, I'd love the link please.