I have the same issue with the Garmin Dual. Somehow it works now. What I did was letting the HR strap connect to the phone. Then I went to BT from the phone and kicked the HR from the phone again. After this it worked in TR. I don’t think its a TR problem as I experienced the same issue with the Xert app. But everytime the message to pair comes up on the phone, I cancel it. I tried a few times to pair , but this broke it again.