Landscape's materials don't work (can't add materials to landscape)

Hello, has anyone come across this problem:
Can’t add any material to the landscape, it just doesn’t render the textures. I tried to download different materials from different sites, but the same thing happens all the time: they are first displayed in the viewport with folders, but when I overlay them on the landscape, they just lose their textures, and already on the landscape itself there is just a glowing material without textures



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