The door wont open when the shop is open but only when the shop is closed it will open.
bugs on DOOR
I don't really know how it happens or how to fix it, but it's been brought up before - Try constantly opening it and closing it and trying to get the sign to be in sync with it
Try sleep/save/quit and reload to see if it fixes itself. - maybe contact the other users on bug report megapost - and see what they were doing when it fixed itself.
I am having the same problem. Its either after I save and exit the game or after I sleep (idk), but when I try to open the door it does not work correctly. The door will only open inwards and make the open/close sign unreachable. However if the door is closed, I can change the open/close sign and but not be able to open and close the door. Its a game breaking glitch. I always have to restart and hope it doesn't happen again.