Hi there,
When in WHITE SPACE, interact with all the objects. Make sure to say "Yes" when opening the sketchbook or else it will trap you in WHITE SPACE until you reset the game. (We are working on fixing this bug in the new update.)
After interacting with all the objects, run around WHITE SPACE and you should be able to find MARI.
Use one of the RED HANDS to teleport back to the starting position and then the door should appear.
Hope this helps!
- KeatonGamer