I have something simular issue, when i open the cominity in the app and subscripe I see a few post, but when i visit the comunity from a browser i see mich more posts.

That makes a lot of sense, thanks a lot!

Okay so after tinkering around I have found the most likely solution!

I just changed country on my VPN, so i guess it was something blocking me. Maybe the prevois VPN server was flagged.