Why does the call go through but no voice over Freepbx 15?

Question

Asterisk

Task:
It is necessary to organize telephony for several rooms, calls only within the local network.

I suppose that a good solution could be to install ip phones (+ softphons where possible), connect them via asterisk or freepbx distro, etc.

What has been done:
I have no experience in organizing ip telephony. Therefore, as a test, I installed freepbx 15 on a virtual machine. The virtual machine currently has a connection type of "Network Bridge". That is, as far as I understand, it is perceived as a separate device in the local network and, in my case, receives ip from the wi-fi router.

Through the web interface, I connected to the server and configured freepbx in accordance with various learning resources. I installed two softphones (one blink, the second linphone), which can now call each other.

Problem:
There were a number of problems that were solved, but I can’t solve one yet - softphones call each other, but there is no voice transmission, only noise when you say something. I looked at many different resources that describe the solution to the problem, but nothing helps.

What could be causing this behaviour? If there are a lot of reasons, give at least some.

My local network 192.168.1.0/255.255.255.0 was added to Asterisk sip settings in NAT settings.
I tried to do something with audio codecs, and much more.

Thanks in advance