Looks like it is hitting iOS as well.
Forum Categories Not Loading

Just updated to 4.0.4 and the problem categories are loading; didn't test again to see if it was the update or something on the back end.

Yes. General Chess and Site Feedback showed "No topics" this morning.
Has anyone gotten an update on this?

I have communicated with @jdcannon a he was forwarding it on to the iOS and Android project managers. That was on Tuesday.
My guess is it isn't a problem with the apps exactly, but the interface/API the are using to pull the content; so really a code issue in the site.
Haven't exhaustively checked all topics, but General Chess Discussion and Chess Books & Equipment aren't loading, just shows No Forum Topics.
Others are having similar issues.
https://www.chess.com/forum/view/help-support/something-is-wrong-with-the-app-forums-46649142
App 4.0.3