I'm using a variety of Polycom phones and I they have recently been unable to provide Music on Hold. It is just silence. I can verify MOH is setup correctly on 3CX, as when I use a voip soft phone, MOH will work as expected. I only recently learned of this issue, and can't pinpoint when it happened so it's tough to find out what changed. But I am guessing it is because of the phone provisioning with the latest version of 3CX supporting Polycom 5.x.x. The phones I'm using are a mix of VVX600, VVX500, IP335. The phones are setup with Support Re-Invite & Support Replaces Header to ENABLED. PBX Delivers audio to DISABLED. I have tried various combinations of enabling and disabling the three options above to no avail. Would anybody have any suggestions on other things I can look into? Thanks.