There's an instruction on the floor as you walk through the first door. I got stuck on it too.
I managed to do it, what i did is walk to the door you progress through and its locked so i turned back and ignored the bathroom door. Went to the start and then it was open, just try that walk straight back and forward and it should open. But im wondering now how do you collect the final photo piece? Because I get them all but then the last one you do in the menu doesn't work for me. Has this not been patched for that yet?