I am a Garmin user and use a Heart Rate chest strap. It will not sync to Zwift and per technical support it is not compatible with the system. Many people are Garmin users, it would be beneficial to have the two communicate to get the best data. My speed and cadence sensors are Garmin and they sync which means the opportunity is there. I hope this gets fixed in an update.
Why isn’t it compatible? Sounds like you’re connecting your accessories via Bluetooth and your Garmin HR strap is ANT+ only. Zwifts supports ANT+ via an ANT+ usb stick plugged into your PC.
I’m a Garmin user also with a Garmin Heart Rate chest strap. For me it works just fine with ANT+ antenne and ANT+ connection. Via Bluetooth it indeed doesn’t work like @Nigel_Doyle states. Looks like it’s more an issue for Garmin rather than for Zwift…
The Garmin heart rate monitor is ant+ only. You can try the wahoo tickr heart rate monitor that’s bluetooth and ant+ together.
Alternatively have you tried to pair the heart rate monitor with your garmin device and then pair the Garmin device with zwift in hopes of the sensors working.
You cannot use a Garmin device to bridge an ANT+ signal to Zwift, you would need to use something like CABLE to do that.