We recently intalled a Valcom IP-based paging system. VIP-201 is the paging server connecting to an NEC SV8100 PBX. The paging is setup as a SIP station port with an extension number.
When we dial the extension from the local plant, the phones give a "SIP Out of Range" message on the display and a high-pitched beeping sound.

When we call the extension from a remote facility (also with SV8100 PBX) through CCIS, it actually pages the horns correctly, no error displayed.

We also have a SIP station port setup for Night Bell, as a different extension number, but still going through the VIP-201. When we call this extension number from the local plant, it rings the horns just fine, no errors.

Could I be missing something in respects to SIP port numbers?

Note: The local PBX is located in Latin America and the "remote facility" is in North America.

Any advice is greatly appreciated.
thanks,
Matt C