Why are skyboxes not showing up in unity?

Question

Unity

Recently I decided to change the skybox in the game to unity and for some reason now they are not displayed, I took them from the asset store, now even the standard skybox does not work, lighting is displayed, and there are no textures with clouds

UPD: There are textures and animations in the editor, but not in the finished one build

Answer 1

It happened with URP rendering, but skybox was not going to be on the server. From scratch, I created an empty URP project on the freshest unit, copied the old one into it, and it began to assemble normally.