I have that problem all the time. The most consistent way I’ve gotten around it is to click on any post within that community. There’ll be a subscribe button in there, too, and that one always shows up for me, unlike the community page’s. I haven’t found a way around this problem if a community has zero posts, so if I don’t have something reminding me to go back, I just forget about it. If you’re finding new ones to subscribe to through New Communities@lemmy.world (or similar), you can save the post advertising the community and go back to it later.

Are you using a 3rd party app or just a desktop? it works okay for me, but sometimes it can get stuck on ‘pending’ when theres a lot of traffic.

If that happens come back later and toggle the subscribe button

If the Subscribe is there but it’s unclickable (if you’re viewing from your instance), create a post and back out instantly see below, it will be there when you go back. Sometimes you have to click it a couple of times and sometimes it says pending which can be a visual bug.

I have some info at the bottom of this post: https://aussie.zone/post/132034

Hay subscriptions from other instances are no problem in the fediverse/on lemmy.

What client/interface do you use? Maybe we can help you find the button :)

I just subscribed from kbin.social. To subscribe I searched for the group from my own instance and found a subscribe button there. The slightly complicated thing to realise is that you are subscribing to your instance’s federated copy of the group- not the original group.

It’s probably to do with how you are accessing it. If it’s a browser, just click the link, don’t ‘open in new tab’ or try a different link.

Other option is to search ‘plants’ of similar and filter by community.