Bkank Materials

Hi there, my classmates and I made a 3d side scroller game and I used the M_rock material to make blocks that looked like a cave that our character would break through… All of the textures are there when making the level, but when you hit play, the blocks look like a grey checkerboard and have no texture. How do I fix this? help is needed desperately. Thanks in advance

a frustrated level builder.