Sennheiser PXC 550 keeps disconnecting from my MacBook Pro 5.5

I recently acquired a pair of PXC 550 wireless bluetooth "travel" headphones from Sennheiser.

Pairing and connecting them with my old MacBook Pro 5.5 works (by pressing the headphones effects button for 4 seconds making them show in the devices list on the Mac) but after a few more seconds the headphones automatically disconnects and I am trying to find out why, do you know?

During the time they are connected they do not show up in the audio settings pane.

Built in Bluetooth used by the MacBook Pro are 2.1+EDR and the headphones are 4.2 but searching they should be compatible.

Sennheiser says this needs to be supported by the connected device, are those supported by a MacBook Pro 5.5?

• Hands Free Profile (HFP)
• Headset Profile (HSP)
• Audio/Video Remote Control Profile (AVRCP)
• Advanced Audio Distribution Profile (A2DP)
• Device ID Profile (DIP)