Materials do not show up in mobile preview

The materials in my game are very simple. They only use base and emissive color. They are all only default lit or unlit. There are less than 16 texture samples. There are no special nodes. They all follow the guidelines for materials on mobile platforms that are in the documentation. However, none of these materials show up in the mobile preview at all. Absolutely 0 textures appear and everything is in the world grid material. Why is this?

I’ve tried to preview on different devices with no difference.