I have a traditional trainer (Blackburn) and am using Garmin speed and cadence sensors.
On the computer unit mounted on my stem (an Edge 25), I’ll see, for example, an cadence of 90 and a speed of 20 mph.
But during a ride on Zwift, although the cadence matches my Edge, but speed will display as about 4 mph.
I’m really not that slow!
The fact that my bike mounted computer shows a reasonable speed for the gearing and cadence suggests that the wheel isn’t and the hub mounted speed sensor isn’t slipping either.
Also, the sensors are both working and sending accurate readings to my bike computer. And the USB ANT+ are apparently doing their jobs (ANT+ is sitting under the bike close to both sensors)
So … any ideas why the Zwift online display of my speed is slow low?