Music on hold (MOH) not working for desk phones

[hccj]

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.

 

[hccj]

Quick update:

I found out that VVX600 and IP335 phones actually do play MOH correctly. But VVX500 phones are have silence in place of MOH.

All phones did work properly when first setup some months ago.

Any thoughts?