Why are you setting the door to sollid in the first place? Solid objects are unpassable, period. You will never overlap with them. At least, not if you're using a built-in behavior like Platform or 8 Direction.
I was confused about that as well. But when I checked his cap I figured that he wanted the door to be part of the level boundary.
Actually wouldn't it be better Makis to be able to place the door anywhere in the level, so the player can overlap anytime, but only pass through the door with the key? In many platformer games doors are part of the background. So you might want to go for that. But maybe your game concept requires this. After all I don't know.
Instead of using overlap with the door object i use collision with another object. Even though the door is set to solid (to prevent the player from passing through the door) it still doesn't work. I'm checking for collision and not for overlaping so i guess it doesn't matter that the door is solid!
You are using collision with another object and not the door itself? But your next sentence kind of sounds like you were still using the door itself just with on collision on not overlap. Again, I'm a little confused there.
EDIT: Oh I get it... the another object thing lol. Of course it's called like that in Construct itself. My bad. Then I guess you can't be on collision with something solid when you're using platform behavior.
Anyway, I made small changes to the cap you posted. It works with offset. Remember if the door was to be approached from a different or both directions you need to have an event with different X offset as well.
Here is the cap