Thanks, MikeOxlong. We have had these radios since around 2012. I'll have to check their firmware version. The portables from the same time frame worked fine. Do you know what version the functionality became enabled? I feel like if there was ever a feature vs firmware conflict in the past the software would say that it was not applicable to that radio, but I may be wrong or thinking of Kenwood products.
And to clarify, yes, these are authorized users on the MOSWIN system. It's for a county sheriff's office that is authorized to transmit on most TG's, but was granted monitor-only access to Highway Patrol TG's. I can program everything myself which saves the trouble and cost of coordinating fleet updates through our Moto vendor, and I got it to work perfectly on our portables, but it's not taking on the mobiles. I tested it on an MSHP TG just to double check my work and when it keyed up I took it back out. MO DPS is nice about letting trusted local agency IT/radio staff have system keys, but they'll get salty about it quick if we key up on the HP Dispatch TG's.