No audio on remote extension


I have Yeastar U100 (I know it is obsolete but client is still using it) at client's site, and he have a remote branch. I have extension in remote office which is registered via DDNS in router. 

Extension register correctly but when I make call and session started there is no audio, on both sides. 

This is SIP settings in U100

Also NAT settings are as follow

As  you can see from screenshot below extension 101 is connected

And I am able to make calls which you can clearly see in CDR

But when they start session we  there is no audio. you can see there has been billing time but we couldn't talk.

In Huawei router we have set port forwarding as follows

And SIP ALG is set as follows:

I tried turning firewall of (on U100 and router both), tried to use DMZ and still no result, I tried buch of other things too and still no result.

Does anyone know how to solve this mistery?

Thanks in advance for all of the help.



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