Can't convert height select back into 3D shape

I’ve been having trouble returning the output of any selector back to solid 3D. I’ve seen it done in the example files, and even copied some techniques to the letter, but still end up with a flat black and white image, whereas the sample is shown in 3D. Please help, it’s driving me crazy!

Right click on the node, go to output hint, then select terrain

Thanks Delta. You’re a life saver.