Thank you for the quick reply. I think your suggestion helped me progress with my problem. The extent of my DEM was larger than the other input files. I reran with a smaller clip of the DEM and now have an output file. I am looking more closely to see how the output DEM turned out. It is not quite how I would expect. Does the input vector roads file need to be a continuous road network?
It is good to know about the WhiteBoxToolsRunner. It looks like that would allow a method to run the tools in mybinder. Is that correct?