These settings should be correct
ip=172.31.1.100
ip_local=172.31.1.100
Please remove duplicated 'codecs' setting.
First setting is correct:
codecs=opus,alaw,ulaw,g729,speex16,g722,mpeg4-generic,telephone-event,h264,vp8,flv,mpv
Restart WCS server to apply changes.
service webcallserver restart