I dont really recall that door being locked during my time there. Upon enter maxos temple, you will see a main door with a pedestal in front of it. Read from pedestal and there a urn on the right side of the door where you can interact. Just interact with it and its done. Then just open the main entrance door and will be in the room with the 3 doors. During my game, I didnt find them lock up at all. You seems to have finish the platform jumping and gold trial. The only left now is the mirror test. Try go interact again with everything you can touch in the room, include the urn at the main door entrance.
