If you want to play multiplayer after playing extinction solo with this trainer, make sure to close the trainer and restart the game(exit the game fully and open again). I've noticed that even if I just close the trainer, I'm still jumping high in multiplayer(gets a bit glitchy). I had to immediately close the game(exit game) and start it again.
So if you're getting banned, it could be possible that you're not restarting the game and instead heading straight to multiplayer.