Certain sets of criteria and circumstances may cause an Ops Team Member to receive an error they are "Unable to Add Partner, Relationship Already Exists".
You will receive this error if the relationship name already exists. Relationship names are unique values.
Check for existing relationship names and ensure the name is unique.
Note: If you still receive the error, and are unable to view all existing relationships there may be a unique relationship name not visible to your user account. Please refer to the linked article to reset the Ops visibility privileges.