Fenix 5S - shows no cadence data with Power2max crank

Anyone else having a similar issue ? I have a Powerbox (Power2max NG) crank. It is Ant+ and I have also just paid for the bluetooth upgrade.

Ipad picks up cadence / power OK, with some occasional pairing issues. Garmin 800 always picks both cadence and power up with no issues. However ! I cant get any cadence power to show at all on my Fenix 5. It sees the device as a power meter, but when I search for cadence sensors, it comes back with nothing, over both ant+ and bluetooth.

Any ideas ?