If the only member of the team is an inactive participant, you will reach this error. You will need to make the participant record active in order to disband the team.

To reactivate the team member, follow these steps:
  1. Manage the TeamRaiser event.
  2. Search for the member of the team that is inactive.
  3. Select the Make Active link.
To disband the team:
  1. Visit the Teams tab and search for the name of the Team.
  2. Select the Disband Team link.
Once you have disbanded the team you can mark the participant as inactive.