Our tech has installed the external moh device, but nothing is playing on-hold. Is there additional programming that needs to be done?

yes, you need to go in and tell the lines which music source you want to hear.

you can turn backgound music on on a phone and select the source you want to hear. this is a good way to verify which source it is hooked up to. you do this through the diplay of the phone.

Are there certain codes the tech will need to know to do this? I have a feeling he is not very familiar with Comdial systems and may need to know the exact path.

is the tech programming the system from the phone?

I suggest you use the VMMI software.

I am sure there is a way from the phones, I just have never done it.

If this system did not have MOH to begin with, the installing tech may have programmed the system for "tone on hold". I would contact the installing company and ask them to dial in and make a program change.