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?

Sorry if this is a stupid question.