When painting my landscape I get that error and it gives my landscape this untextured block. I have auto grass in my landscape material.
SOLVED: “From the looks of it, you might want to try selecting your Texture Samples within your landscape’s material and set the Sampler Source to Shared:Wrapped to see if that resolves your issue.”
What if its a texture object?
I hope this work as it worked for me, first save and restart UE5. Then cover that square with a single material that works, use a large brush, it will look like it does not work at first but once I covered all the square the sucker just popped back into life and I did a little dance. Then your other materials should work and if they mess up again repeat this process. I got mine to a stage that works so I am leaving it alone now.
I was about to rebuild my material again, so glad I did not have to.
Simple as that! Thank you