If you are the appropriate level and are unable to queue for an expert dungeon, you may not yet meet the stat requirements. You can find information about the requirements in the 'Looking For Group' interface in-game by following the below steps:
- Open the 'Looking For Group' UI by pressing 'i' by default
- Look for the lock icon within the section you are attempting to queue for
- Hover over the lock and the stat requirements will be listed in the tooltip
Once you reach the required stats to be able to queue, this lock should disappear and a 'JOIN' button will appear. If you have reached the appropriate stats (without buffs) and still cannot queue, make certain that all your soul points have been spent in all your roles and switch back and forth between them to be certain.