I am new to using Hammer can anyone explain why this is happening?

[Natepacito]

For context, I am trying to make a Koth map, and I noticed that some of the props including the Koth capture plate appear as an error. am I doing something wrong or is this a problem with Hammer itself?

 

[Sonoma]

try verifying the integrity of the game files

After that go to the Options Menu in Hammer and make sure the Team Fortress 2 game configuration is correct