Subtitled: Why error messages are good.
Came up with another error while running TopoToRaster but this time ArcGIS gave an error message that led to a solution. Turned out all my contour lines had an elevation of 16 which TopoToRaster did not like. I had intended to increase the elevation and inadvertently set them all to sixteen. I had saved the previous values before editing so it turned out to be a simple fix and I didn’t have to spend a day trying figure out what was wrong.