There are several reasons why you might have trouble joining a rally. Here are some reasons below:
-The rally is closed and requires an invitation - ask the rally leader to add you if this is the case.
-It is possible to join the Facebook group and not be joined in-game. You might just be stuck in one but not the other. We recommend removing yourself from the Facebook group, then trying to rejoin/be reinvited to the rally a second time. It usually works!
-You are still a member of another rally - leave the rally you are in before trying to join another.
-You just left another rally (you need to wait 24 hours)
-You left your rally but are still a member of the Facebook group of your old rally - remove yourself from all Facebook rally groups.
-You used to be in this rally - Facebook doesn't allow people to return to rallies they have left sometimes, it's a weird rule. Same if you were booted out. There is no fix for this, so you may have to join another rally.
-This rally is full. Wait until there is a spot available.
Check to make sure you are not a member of any of these groups. You may be able to join a different rally!