For some strange reason my characters isn't getting any xp after finishing a mission/quest battle and they havn't reached max level yet even those that is still level 1 don't get any xp.

Do you receive crystals ?
When your fair-play status is bad (basically you have a small red triangle beside your pseudo in the room), you gain less crystal and less XP at the end of each game.
And less means you can receive 0XP and 0 Crystal.
To change your status, you have to play the games until the normal end (no quit, no time expiration) until you receive the standard reward.