Have you tried rebooting the watch? Unpair first, then reboot and then re-pair.Yes and no.
The sensor is connected with ANT+ to my Wahoo. But I connect to WOD first then I switch the Wahoo on.
But did works fine since the last few months. That was not the problem.
If that doesn't help then try a short test workout (over 1 minute) where it fails to connect and then send the wkt file for that workout to info@workoutdoors.net and I will take a look. As usual, to do this tap the Export buttons 3 times quickly.