Poster Disappears after Copy and Pasting it from another map into my own

[Potassium]

I tried to take the large poster of the map of the world from the big room off the side of the intel room of 2fort and put it into my own map. When I do, the poster shows up in hammer but doesn't when I actually run the map.

 

[Kill_the_Bug]

is it a model or an overlay? Overlays will give you issues. If it's an overlay, look it up then use the overlay button