When adding the Super Compliance Officer (SCO) or Compliance Officer (CO) role to a specific user via API, the following error message may be displayed (Figure 1):
Figure 1 Error
This error means you are trying to add the SCO or CO role when the user in question already has that role assigned to them. If you would like to demote or promote the user, you need to remove the role they currently have first and then assign the new role.
Refer to the Knowledge Article found here for more information on how to remove a role from a user.