When you drag the key onto the door, it means the door is already unlocked. To enter the room, you still need to press the Space key to interact with the door. All interactions in this game use the Space key.
I’ve just tested it on my side, and I didn’t encounter the bug you mentioned—it’s likely that you just weren’t standing close enough to the door when pressing Space.
Thank you for playing, and I’m really glad you like my game.