Hi,
I have the same scenario, and i'm facing the same problem. Using the debug on the VG, i can see that the digits are unable to be sent, disconnection cause code:65.
As from the NEC side, when a phone tries to dial, i can't see any logs on the VG, as if their not signaling between the two.
I have asked the NEC team to assist us in this, waiting their reply.
Please let me know if you find anything.
Regards,