Support unable to de-register device from previous owner - Can't now join the new beta programme

I have been using the betas for a while now and went to try and register for the new process. When attempting this I get the below error:

BETA SOFTWARE PROGRAM
Unable to Complete Enrollment

This device cannot be enrolled in the Garmin beta software program at this time. It may no longer be receiving beta software, or the maximum number of enrolled users may have been met.

I contacted support via chat and they can see as it was a pre-owned purchase it is still registered on someone else's account, support can't/won't remove it as I am not that account owner, even though I am the device owner...I'm trying to get in touch with the previous owner but nothing yet, am I out of luck?