It sounds like a mismatch where the Quixel master material (the sample parameters) is setup for non-virtual textures, while the texture being set in the material instance isn’t.
If it says “Sampler Requires non-VirtualTexture”, you need to open the texture and turn off “Virtual Texture Streaming”. (Virtual textures will say VT.) The Quixel master material is setup for one or the other.
In Project Settings, when you enable VT, there’s an option to automatically import textures as virtual which is on by default. So new Quixel textures come in virtual while the master material is set as non-virtual. It’ll look blurry and you’ll have errors in the material instance. You’ll want to turn this option off. (However, Quixel seems to ignore it.)