Issue with VOIP incoming calls

[hmalakooti]

Hello Folks

we have an in house Allowrx SIP device which is behind our firewall

Outgoing calls are fine but no one can make any incoming calls and it goes to voice  mail

here is what already done , In Exception part of  Inspection setting , we have made an exception to bypass any protection from SIP device Source IP. Assigned static IP to SIP device . Application filtering and Network blade SIP device 's IP is allowed to communicate with babytel (that's where outgoing calls work )

SIP provider asked us to check bellow criteria , any though about checking these items or solving the problem is much appreciated

NAT Consistency" must be activated

"SIP transformation/SIP ALG/SIP Helper" must be deactivate

"UDP timeout" should be set at 300 seconds.

"UDP flood protection" must be deactivated.

 "SPI(Stateful Packet Inspection)" must be deactivated.

Thank you

[PhoneBoy]

To provide precise answers to your queries, version/JHF level would be required as well as precisely how the gateway is being managed.
A network diagram showing the gateway and your SIP device(s) would also be helpful. 

It would also be helpful to get precise definitions of NAT Consistency and SPI from your vendor to ensure we're talking about the same things.