I believe the game only allows a max queue of 20 so when you try to join, it will give you a "server is full" message. I'm having the same issue as we speak. The way I got into the queue was by refreshing the server page every couple minutes waiting for the queue to drop to 19 then try joining.
thats correct the max queue is 20 (which is rare) so when that happens none of us can join. Just limitation with DICE games. Same thing with BF1 and that has a max queue of 10.
As Marcos said, once it goes down to 19, you can join bypassing the rest of the line.