In your server log (server.log), you may see the following error:
Associated object already exists in database with GUID:...
Here are some common causes for this error:
The Data Collection Service driver was removed and re-added/ When you remove the Data Collection Service driver, you must also refresh the database. Otherwise, the new Data Collection Service driver will attempt to re-add the objects that already exist in the database.
There is an overlap in scope between two Data Collection Service drivers. They are both trying to synchronize objects in the database.