How do I keep a brand new one of these mats from wanting to keep curling up on the ends?

Its been a week of putting a 1x2x3 board on it with weights and it still wants to curl up. I don't want to use duct tape. I have to move it to mop so fastening it the floor is out. It is commercial grade and idk why it wont relax on the ends.

(This is a stock picture of the same mat.)