That all looks right. I presume your Draw Material isn’t using collection parameters? They should look like this:
Could you go to where you are doing the LineTraceByChannel, and where it says Draw Debug Type on the node, change that to For One Frame, when you try draw you should see a red dot appear where the drawing should be happening, if you don’t see this then the trace isn’t set up right.
edit: also check that the default values aren’t too low on those variables, strength 1, strength .1 or so. In Cube blueprint.