area portals showing up as black solid black textures in source maps

[KarateWalrus]

Hello,

Pretty new to areaportals on maps and map-making in hammer in general. I make them and then it just make a black textured wall wherever I place one. Any ideas? I followed this video. Anyhow, any help would be appreciated.

https://www.youtube.com/watch?v=uOOJkk8-OUw