That means there is a software mismatch between ACC and digital card. The ACCs are backwards compatible -- an ACC5 will work on MCS250.
The closest I have er come to finding pre ACC4 is this:
https://www.ebay.com/itm/374240119673I’ve seen those “Teradon” units before and never quite known what they are supposed to be, as they don’t quite look like the Dukane quality of every other piece, and there’s no reference to them in any documentation I’ve seen.
The issue I’m having in regards to the menus I figured might have something to do with the ACC.
The CCU software version is 4.05 as it’s a fairly recent MCS350 digital card, however I only have an ACC4 (first revision) and ACC4B. I have ordered an ACC5 in hopes it will solve the problem. It’s the menus for Program Tones, Program Inputs, Program Outputs, Call-In Mode and Call-In transfer that are not coming up on the ACC.