Typically, when that happens to me, it's an indication that I'm about to lose connection to ZOS server. Short moments later, my game just crash, and I would have an error, something about not having internet connection. Oh, I do have internet connection because I still have connection with my laptop. It's a matter of relogging in from the character screen. If after logging in this way doesn't fix it, I would close application completely and restart the game process. It would generally reset then. Sometimes, if I roll out, backward, forward, whatever, it would reset.

You can also try to wayshrine/travel to a different map zone. Sometimes, that can fix it. However, if you're have tried reloading and stuff and still not fixed, then try submitting the in-game help/support option.