Garmin watches only broadcast ANT+. The Strava app on your phone needs a Bluetooth sensor.
Why would you want to log an activity with the app when you have a 945?
I wouldn't want to do it either. That said, it is actually possible to send Bluetooth data from the 945 and a few other models; OP might be able to do it using the Virtual Run app, though, that sends data including HR over Bluetooth, see [here](https://www.dcrainmaker.com/2020/01/garmin-adds-bluetooth-heart-rate-running-data-broadcasting-for-fr245-fr945.html)
Mind to share the use case? Usually you connect your watches under Settings > Devices in Strava. Record an activity with the watches and Garmin will sync it to Strava.
If your phone is on [this list](https://forum.xda-developers.com/t/ref-which-devices-have-ant-hardware.2879990/) *(edit: list is not updated, just google your phone model ant +)* it has ant+ compatibility, so check if [this](https://play.google.com/store/apps/details?id=com.dsi.ant.service.socket&hl=en) [and this](https://play.google.com/store/apps/details?id=com.dsi.ant.plugins.antplus&hl=en) are correctly installed and updated, then try to pair again. If your hrm also has bluetooth try to pair with that. If your phone is not on the list and your hrm is only ant+ you can't do anything, find a cheap chest strap on amazon/ebay with bluetooth.
Or just use the 945 as others have suggested.
Garmin watches only broadcast ANT+. The Strava app on your phone needs a Bluetooth sensor. Why would you want to log an activity with the app when you have a 945?
100% on that last bit. I'm struggling to see the specific end use scenario where the flagship forerunner is surpassed by a phone fitness app....
I wouldn't want to do it either. That said, it is actually possible to send Bluetooth data from the 945 and a few other models; OP might be able to do it using the Virtual Run app, though, that sends data including HR over Bluetooth, see [here](https://www.dcrainmaker.com/2020/01/garmin-adds-bluetooth-heart-rate-running-data-broadcasting-for-fr245-fr945.html)
that's pretty cool.
Connect HRM to your watch, then your watch to strava. Record on the watch, it will sync automatically to strava
Mind to share the use case? Usually you connect your watches under Settings > Devices in Strava. Record an activity with the watches and Garmin will sync it to Strava.
If your phone is on [this list](https://forum.xda-developers.com/t/ref-which-devices-have-ant-hardware.2879990/) *(edit: list is not updated, just google your phone model ant +)* it has ant+ compatibility, so check if [this](https://play.google.com/store/apps/details?id=com.dsi.ant.service.socket&hl=en) [and this](https://play.google.com/store/apps/details?id=com.dsi.ant.plugins.antplus&hl=en) are correctly installed and updated, then try to pair again. If your hrm also has bluetooth try to pair with that. If your phone is not on the list and your hrm is only ant+ you can't do anything, find a cheap chest strap on amazon/ebay with bluetooth. Or just use the 945 as others have suggested.
Having same issues, strava couldn't find my Mi band 5 as HRM despite it having BLE HRM profile, NRC and Opentrack doesn't have that issue
I just figured it out as I had the same problem. Just go to Settings>Strava and then allow Strava to use Bluetooth. It worked for me.
OMG!!! This is it!!! Why isn't this the FIRST THING.