Hello All!
When I moved last summer thought the car was a safe place to transport my cutting mat. Wrong if it is not removed very soon. It warped badly. Just laid it in the drive way or front step in the hot sun two or three days, hottest part of day. Brought it in overnight and laid flat. If warm when you bring it in lay flat. Not a ripple after that. It is a Fiskars and I have had it for several years. Possibly different material than mats are made of now. As mentioned, try different things if you cannot use the mat at all.