My guess is the 'privacy' was off that co and then somehow got put back on.
Sorry, don't have manual for that one to give you the proc/code to put it back on.
I'm sure someone will chime in with it.
P.S. On the 1232-11 from that era one would press the co line they're on -releasing privacy for 5 seconds..causing it to flash green for 5 sec's...then someone else could join in by pressing that co..as long as they did it within the 5 seconds. Not sure if that works on your 308.