Can't add router to RMS

Even though I have credits, I can’t add a specific device to the RMS. I would like an official support email to send the device id and information. I have already checked that serial and mac address don’t exist already (I have 307 registered device and I’m quite experieced)
When adding this device I receive the error Device with … at line 1 could not be added…
Thanks.

Hello,

To investigate and troubleshoot this matter further, I’ve sent you a form to fill out. When completing it, please use 11878 as the ticket ID. Once submitted, we will be able to contact you privately to delve deeper into the issue.

Kind regards,