TeamSpeak 5.0.0-beta31 – Announcements – TeamSpeak

As @Alligatoras said, they are shutting down the servers, presumably only temporarily, and thus disabled the option to see it in TS5.
You still can see it in TS3 as they can not quickly disable your bookmarks partially.
You only can still connect via TS3 as they didn’t shut the server down yet.
They probably didn’t expect beta users to still use TS3…