Team assignment (selection) is removed

Your teams can be deleted if your settings were to assign them by the way of Participant List (PL).

If you delete the participant list and import or create a new one, your original team assignment will be removed/deleted. 

Therefore, you have to go back to Tools --> Settings --> Team Settings and choose your team "Assign by" settings once again.

Remember, that you can only set your teams in a Participant List if you use a close-ended descriptor and create the values for the Team.

For example, the Team descriptor may contain values: Phillies, Flyers, Eagles, Steelers (if you're in PA, like us :))