Why does the tacx app not allow me to add my HRM to my Neo 2 screen. But dies to the demo mode.

I have a Tacx Neo 2 trainer.  When I load it up it is OK.  But it will not allow  me to add my Garmin HRM to the neo 2 on the app, to do a course.  But it will allow me to add it in demo mode.  I have tried going in to Device manager but still it will jot add it to the Neo 2.