Walls not showing in game

[DanielRand47]

Hey everyone. I have a very annoying problem. So when I add any new objects/duplicate, they do not appear, even though they appear in the editor window. I have also checked the HTML file that holds all the data for the map, such as entities, decals, lights, all that fun stuff and everything is there. However, when I enter the game, the wall is gone. It's as if it was never added. Now in a new map, it does show, but not the one I'm working on.

If anyone has experienced this issue and knows a quick fix, please let me know.