Polycom IP6000 can make calls, but get fast busy when calling that extension from within the local network

Very odd: I can make calls from our Soundpoint IP 6000. No problems, and all is good.
But, we can’t forward calls to the extension (or even place a direct call to it) from other phones on the local server. It can call other phones though. Additionally, the OSS Endpoint Manager shows the phone as being offline (even after a rebuild). Very odd. Has anyone seen this kind of issue with this model before? Maybe I need to spring for the commercial Endpoint Manager to get updated profiles?

And magically, it finally started to work as it should (over a day later).