Off the top of my head I believe Refused is for when an item is disabled or does not exist in the database. Denied should be the TG and/or Radio ID are not permitted at the site, but the TG or Radio are valid in the system.
I'll have to pay attention next time I have PRO96COM running when I'm working on a system.
Or just wait until he reads the thread, and chooses to reply. No sense giving someone more email to read.
Ultimately PRO96COM just recites what the standard dictates. I know I've seen some odd questionable conditions where radios are denied or refused (unrelated to affiliation) for features that don't exactly match what's happened based on the vendor's event, but at the same time the standard has to be vague in an effort to support multiple vendors.
To be honest I'd have to look through the code to remember the difference between them. As far as affiliation is concerned, a radio is typically denied if the talkgroup is not allowed on the site in question. It usually doesn't have anything to do with the Radio ID at that point.
Refused according to the TIA docs is defined as the Group Address is invalid and that the
SU need not enter control channel hunt and the SU may attempt to reaffiliate
after a user stimulus.