Fill layer problems

Hello all, new here, looking for help with an issue. Take a look at this video and fast forward to 1 hour 50 minutes. He rights clicks on one his layers, adds a weight blended layer, then does a fill layer and his landscape takes on that material. Mine doesn’t, and attempting to paint manually with the layer does nothing (stay grey and black checker).

What am I doing wrong?

Thanks in advance for your help.