Issue with AMF on iOs

Hello,

While developping a mobile application using flex 4.15 with the latest AIR buid I get the following error when the application calls  a service method on iOS :

[RPC Fault faultString="Echec de l'envoi" faultCode="Client.Error.MessageSend" faultDetail="Channel.Connect.Failed error NetConnection.Call.Failed: HTTP: Failed

- It works on android or on the iPhone simulator but not with an actual Apple device.

- It works  on iOsi f I use AIR 16 instead of AIR 21.

Any Idea ?

Thanks.