I am using a Garmin Fenix 7S to record data from the Zwift Hub trainer. I am not actually using Zwift, just the Hub as a trainer. All power data seems to be fine, but the HR just shows —. When I disconnect from the Zwift Hub, the HR shows fine. Why does the HR disappear when the watch is connected to the Zwift Hub? I am connected to the Zwift Hub via Ant+.