Why are the servers empty in APB?
Find the “Show Recommended Only” box, and that will help you find districts that are one threat level higher and lower that you can join and play in. Unfortunately, there isn’t an automatic queue, so you can wait in an empty district, or wait it out until a spot opens up.
I’d advise you to leave “Hide Full” unticked, because you won’t be able to see the active districts. People rarely join the districts that contain less than 10 players. If there are only a few instances, then that means they are currently experiencing issues or the districts just restarted and people are just starting to rejoin them. Be patient!
Also, from time to time, you might see a player typing in /district chat announcing that something special is happening in Social District. This is usually a trick to get you to leave your spot in the current server because it is full and they want their friend(s) to join.