Are you still using that cat5 type cable?
Reading the other thread , I assume no issue of software versions?
Oddly enough I have a job to goto where someone has trouble adding on a rio, all new apparently but they say the panel won't add the Rio in the first place
I just wonder did you add and remove the Rio and it's an old message ,aybe do a 17 restart and might clear it
Dudes what can be measured on the data line and can it be scoped to look for anything , just a thought