This one was very frustrating. My SIP phones could log into the SBC-E and got dialtone fine, but wouldn’t pull PPM. The Avaya One-X Communicator for iPhone could do it though. Whaaaaa??
I have my phones configured to pull a config file from a web server – it’s the only manual setting required in the phone. All other settings are in the config file on the web. Well, it turns out that the phone didn’t like the SET CONFIG_SERVER w.x.y.z parameter. Once I removed that, then PPM flowed just fine.
By the way, if you have trouble with feature buttons, the other issue I had was the entity link between Session Manager and the SBC. If your’re using TLS connections between the phone and the SBC, then you also need to use TLS on the entity link between the SBC and the Session Manager, and the Session Manager to the Communication Manager. In other words, all connections from the endpoint to the CM need to be TLS. If any of them go back to unencrypted TCP or UDP, then the PPM breaks. At least it did for me!