Cannot connect phone number via SIP Trunk in Vapi

Hey. I’ve been trying to connect a phone number to Vapi using NEXION Networks as the SIP trunk provider, but I haven’t been able to get it working.

I did everything as described in Vapi Docs - firstly I create a SIP trunk credential in Vapi, then I associated a phone number with the SIP trunk and then I set to forward calls to {phoneNumber}@<credential_id>.sip.vapi.ai inside the provider. I also allowlisted the necessary IPs.

I see the Sip trunk connection in integrations, I see the connected phone number in the dashboard and I set calls to be forwarded to Vapi assistant. Still calls are not connecting.

Questions from me:

1)How does Vapi register to a “byo-sip-trunk
2)What is the format of the SIP user i.e. does it include country code and + sign?
3)Is there any way to see if Vapi has successfully registered to our trunk?

Thank you in advance for your help!
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