Hi all!
We have found the reason why Whatsapp video/audio transfering does not work.
The reason was on Firewall (FortiGate) we enabled applecation control and allowed on our DC only Azure and DNS applications and 53, 443 ports.
Before we did not enabled application control on DC and everything worked, whatsapp also.
After enabling application control we have seen that WhatsApp tries to send via 53 port Whatapp Filetransfer application signature via Domain controller. But it must only send DNS request and after send traffic via default router.
FortiGate explained that signature as "trying to avoid firewall rules".
We leaved it enable and not allowing traffic.
Please, be aware about working of Whatsapp Application via domain infrastructure.
Best regards, Asset