Mopidy Discourse

No sound when streaming from iOS [snapcast]

There is no sound when I stream music on IOS [Mopidy-Iris snapcast]
PC and Android are works well , there are no errors in the mopidy server log

[audio]
output = audioconvert ! audio/x-raw,rate=48000,channels=2,format=S16LE ! wavenc ! filesink location=/tmp/snapfifo

ubuntu 20.04 LTS
IOS 14.4 iphone 7 plus
browser: safari