Heart Rate not shown Bluetooth (Garmin HRM-Pro)

I connected my Garmin heart rate sensor to the app and it says “connected”. Unfortunately it does not show my heart rate, it just displays 0. I tried to disable and enable Bluetooth and checked for updates, but nothing worked. In other apps the sensor is working as expected.
What else can I do?

Garmin HRM-Pro
iOS 15.4.1

Hi, this is strange. I can only assume Garmin uses standard HR Ble so it should work. You don’t happen to own any Android devices you can test with do you?

No sorry I don’t… it is really strange. Maybe I can test it tomorrow when my partner visits me.
Is it somehow possible to pair the Apple Watch with TrainerDay?

Ok, yes I was thinking testing on Android would be good but also Android is much easier for my developer to find the problem. Sorry no Apple watch support. I will try to research this Garmin a bit more to see if anything pops up.

Just tested on Android and we are facing the same issues.