Lemmy apps don't appear to work well with Lemmy.world
When I started using Lemmy I joined Lemmy.world and downloaded several Lemmy apps, to find one I liked. After a short while, the apps seemingly became incompatible with Lemmy.world and refuse to display the communities I'd joined, or show any content on the main page of the app if I selected Subscribed rather than Local or All. I also couldn't see posts I knew to be there in some communities. Due to these issues I tried Lemmy.ml and fortunately it doesn't suffer from these problems when using the apps. What's going on? Is Lemmy.world broken?
I'm not sure if it's the same thing, but there seems to be some login problems with Lemmy.world (I've been experiencing those for the last 2-3 days when trying to log in from a browser).
Recently lemmy.world and other big lemmy instances were compromised - attackers used an exploit to steal admin JWTs (json web tokens), and started changing settings and posting as admins. JWT is created when you log in, and is passed during all interactions to prove who you are.
To recover from the compromise, lemmy.world invalidated all the existing tokens and forced everyone to log in again. Unfortunately lemmy.world stopped trusting valid JWTs too, and apps all had some crazy behavior.
This was resolved as of Wednesday some time, I think.
My advice is to make sure your apps are all updated, and log out / back in to each of them. If it’s not resolved for you, try deleting and reinstalling the apps. If it’s still not resolved, search for a lemmy support community as another poster suggested.