I can subscribe to only one sub on mander.xyz [workaround]

Update: I can subscribe from a post, but not the community main page.

Old Post:

I had no trouble subscribing to this mader.xyz community:

https://programming.dev/c/science_memes@mander.xyz

But when I went to other communities on mander, the subscribe button was turned into plain text and I could not click it:

https://programming.dev/c/science@mander.xyz

Does anyone have any explanation why? Does mander.xyz limit programming.dev accounts to one subscription?