I have 7975 registered on CUCM 6.1.5. And no MOH only on this device type. On other (7941, 7942, 7962) I hear MOH.
On CUCM MOH was set as unicast and as multicast, no difference. Only on 7975 I hear silence. Diferrent audio source tried to use. Nothing...
All other device type works fine.
What problem can be?