I'm having this exact problem with my edge (described in the first link) but the only answer here didn't work. I'm using a 1030+ with a Saris H3. I tried calibrating immediately after an hour long trainer ride so I can't imagine how much warmer it could get. The first attempt to calibrate immediately fails and the second retry won't calibrate for "tempreture too low."
https://forums.garmin.com/sports-fitness/cycling/f/edge-530/264318/calibrating-indoor-trainer
The following link also describes my problem but no real solutions offered, I'm actually ditching Zwift so I'm wanting to use my Edge exclusively to control trainer. https://forums.garmin.com/sports-fitness/cycling/f/edge-830/215220/can-t-calibrate-indoor-trainer-sensor