Cannot get door back on

I have a new Whirlpool double oven. We got the lower oven door off as in the instructions, but the hinges did not remain at a 45 degree angle. They popped back to a 90 degree angle, as when the door is attached and closed. I can’t get them back to the 45 degree angle to reinstall the door. When we try to install the hinge into the slot in the oven and slowly open the door toward 45 degree angle, they pop out of the slots and return to 90 degrees.