SIP phones is not working but IAX works

Hi Everyone,

I had a working Asterisk with 10 SIP hardphones & 2 IAX phone connected in 2 offshore office and 4 SIP hardphones & 2 IAX phones in NY office.

This happened 2 days back

  1. All hardphone SIP phones in offshore office got disconnected from Asterisk
  2. I cant make outgoing calls from SIP phone in onshore office
  3. All incoming have one way communication
  4. Though my associated DID works its just a one way communication

The following seem to work

  1. IAX phone if offshore office are registered and it is working fine. Communication b/w SIP & IAX are two-way and works well

I checked with the provider in my end 5060 seem to be working but I haven’t checked with provider in my offshore office.

It will great if someone give me hints where to troubleshoot this issue