Im having some problems using the zephyr heart monitor which I bought yesterday

It has had a full charge
I have paired it successfully with the n900
Under settings in Ecoach it lists 'HXM003433' in the device section as my heart monitor, but I have tried two training runs, and although Ecoach records my journey, I have no data for heart rate
I have configured the setttings and then Im selecting new activity, name it and then press record.
Is there a step that Im missing - do I have to tell Ecoach somewhere to record heart data?
I have never used a heart rate monitor, so just to check, it is the fabric from the chest strap that has to be in contact with the skin? Just to make sure it is not a silly error like that

Any ideas how I can troubleshoot this?

Many thanks