This is caused by the username for the Sphere Connector.  Please ensure the username is active. 
  1. In Sphere, Navigate to Control > Administration > Manage Users
  2. Edit the username for the Connector
  3. On the FUnctional Access tab, change it from Inactive to System Administrator: Full Access.
  4. Save changes
  5. Wait a few minutes, then click on the Scheduler again. You should be able to finish your mapping and/pr initiate a sync.