Bluetooth device "connected" but no sound!

I setup and paired bluetooth with Sony MDR-XB650BT : “Bluetooth connected” but no sound !
Volume OK, several sites and sources… battery level OK…: no sound at all.
By the way : the sound output via 2.5 jack and loudspeaker is OK. Just bluetooth without sound !
Thanks for Your great help.

Did you set the bt-device as the output source for the sound source?

If you use pulseaudio you can use pavucontrol check that.

OK, vefified and seams to be OK, connected, input output levels OK… but no sound !!!