This error occurs when there are more than 2 responsible signers tied to a student. Smart Tuition contracts only allow 2 responsible signers per child.

To remove a responsible signer:
  1. Navigate to Enrollment Management > People Finder - search the student
  2. Click the Contact Card tab
  3. Scroll down to Relationships and click Manage relationships
  4. Under the Responsible Signer column, uncheck all but 2 users who should sign the contract
  5. Click Save