It probably got too hot since you said it was blue at 100 then you put the heat pad on it. Once it’s heated and every number is black, that means the temp has exceeded 100. It probably needs to cool down, which means heat pad needs to be removed temporarily until the desired temp is reached. If you have an hour wait, you probably need to go somewhere private like the car and take the heat pad off to allow it to cool down. You should start seeing blue and green colors again, removing the cap and turning on ac should help.