Garmin Coach syncing to Edge not Forerunner

I'm trying to set up a running plan on Garmin Coach, but cannot seem to get it to sync with my Forerunner 945. Instead, the plan seems to only want to sync with my Edge 1040. I have the Forerunner set as my Primary Wearable and the 1040 as Primary Training Device, but these don't seem to be changeable. Any thoughts or suggestions welcomed!