Sorry for late replay i was travelling. Anyway i got a new pi4 and done all the installation again.
Airplay now work, the thing is that i didn’t activate the plugin in the audioplayer section. I though that it would have been enough to install it since is not specify anywhere that needs also to be activate.
Maybe is just me not very intuitive and very very beginner in anything audio related but i have the feeling that max2play can improve a bit the instruction guide 🙂 I read at least 4 about multiaudio system and for a beginner, they all lack of a deeper explanation.
But again, maybe i just look in the wrong place.
Thank you again anyway for your answer!