Some communities in other instances appear as completely empty (0 posts, 0 subscribers) while they're not

I'm trying to subscribe to communities in other instances but they falsely appear empty. It is not a matter of languages as I see some people suggesting. I have tried choosing English as well as Undetermined without success. Other communities in the same instances appear as they should, without any issues. I have tried from different browsers and even without logging in, fresh browser window, with cleared cache, I open Vlemmy, search for those communities without logging in and I get the same issue. Communities belong to different instances, I can access everything through Lemmy.world although said communities are not in Lemmy.world