I have a problem with Asterisk AVPF settings for WebRTC

Latest Flashphoner Web Call Server 3 does not require AVPF support in Asterisk.
You can use standard configuration without AVPF.

WCS3 will communicate with WebRTC(Browser) by SRTP/AVPF
and WCS3 will communicate with Asterisk by RTP/AVP

So, you do not need to setup AVPF in Asterisk.