Skybox is always pink

Hello, I have a project that is almost complete, however I made the mistake of deleting the skybox material by accident yesterday. The project had a working custom skybox material with a cubemap texture before I deleted the material. I thought I could just remake the material using the image I originally used, and putting that into the windows->Rendering->Lighting settings spot, however the skybox is still pink as if it is missing a texture. I then tried to put in the default skybox material, and found that that was pink as well.

What could cause this? How do I fix it?

Edit: I am using the universal render pipeline