Yes, changing the app from a B4XPage project to a Default one make the thing work. That's the (right) way your app was done.
I don't get the reason (would be curious to know why) but after all, the important is to make the things work
One last issue is to fix is the problem of the "connection lost" (player does not sound anymore) after some minutes when the phone is not used (and the screen black). Any idea on this?
Anyway thanks for your help
Olivier