HRM Dual - BT not transmitting HR

I have given up on my Garmin HRM. Switched to Wahoo and no such issues.  

In fact, my problem resolved after I get the new firmware version 2.50, after getting it both my phones stopped working with it, but aftere I checked Bluetooth settings and removed pairing with the device it start working on both my phones including 1+ 7T on which it stopped working previously.

You may want to check this thread for details: https://forums.garmin.com/sports-fitness/running-multisport/f/accessories-sensors/274997/garmin-hrm-dual-firmware-version-2-50

Now I manage to achieve the same on whife phone, it not reading HR value any more. It looks like once you remove paired device from system it doesn't know any more hov to establish normal paring and connecting any more. Like one value in android register is forgotten to set back do default after removing device from known devices. Also when parring it shortly shows error message that connection is not established, but later device status is as connected.

have you tried to turn off bluetooth on every phone you've connected your HRM chest strap just to make sure that they wouldn't try to "steal" your connection with it?

Yes. This isn't a case. It seems that it have something to do with bluetooth settings. It doesn't want to read values of HR after once you remove paired device and try to pair it again.

It goes something like: app stop responding you try to close it, you loose connection, you try to turn off the bluetooth on phone and turn it back on, and then it stop working.

Second phone was introduced to see if device is working and have nothing to do with stealing a BT connection. I can turn second phone off, put it underground and go different town away and it still wouldn't work....

I can't understand how Garmin can put their name on a cheap Chinese device which they don't support in their app and sell it with such a huge margin. I don't want my money back, I want that it works like other devices which carry Garmin name! This is their promise!  Is it?

This solves an issuue - Reset bluetooth settings

https://gadgetstouse.com/blog/2021/01/04/5-ways-fix-bluetooth-not-working-android/#4_reset_bluetooth_settings

For the coast of loosing all paired bluetooth devices, wifi networks setting and risking of deleting esim (uncheck it before reset). Which you need to connect them again.

Garmin should find better way how to reset BT settings only for HRM Dual. It seems that some BT phone settings stay in register after removing paired device and are not updated on new connection.

I expect fast solution as it seems this is long open issiue (more than a year) which is common among users!

good to know that it solved your issue, I wonder if you paired to your HRM after resetting? Because myself I just delete pairing and eveyrthing is working without it. I was going to advise to just delete it and see if it helps but apparently you found the solution yourself by the time I get in here.

After resetting I didn't pair HRM Dual any more and it is working. But Garmin shoul find the way how to reset phone BT settings for device without the need of resetting all the settings for networks wifi, bluetooth and mobile data network. I use plenty off different wifi, devices,... and it takes too much effort to setup everything back. I hear this is common problem among users of HRM devices! Once it is working other time no...

I noticed what I think was a firmware update for my HRM DUAL, about two weeks ago.  This notification came across my Garmin Edge 530, so I just accepted it.  After the firmware update, Rouvy won't connect with my HRM (via BLE, I believe), although it does show up on the list of devices.  HRM still works fine with Edge 530.  I think Garmin messed something up with the firmware update having to do with BLE...

I had a similar problem with my nordictrack treadmill after the HRM-Dual firmware update.  Ended up fixing with a simple power cycle of treadmill.  Other threads mention having to remove and re-add the sensor to misc other equipment or phones.

Didn't have any issues with it working via bluetooth to phone for Wahoo or RGT Cycling.  Also worked fine with FR945 watch.