How can you verify if routing digits are being sent from carrier in IP Office?

I use Avaya IP Office V5.0
My carrier is AT&T using an IP Flex Circuit for my voice/fax.
I am trying to route incoming faxes to my fax server and forward them using specific phone numbers. It used to work and then we moved and now it is not forwarding DID/Routing numbers to my fax server. I need to verify that I am receiving the routing numbers from AT&T. The Avaya system is set to accept 4 routing digits.
How can I verify that the numbers are actually being sent from AT&T ?
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Run a packet sniffer like Wireshark and troubleshoot the SIP messages at your gateway or Avaya system. You'll be able to see the digits there.

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