I have a DEM (saved as a .tif) and, using QGIS, I want to clip the DEM using a vector mask.
The function will not work.
Am I missing critical step?
If you have the GDAL plugin installed, you can use the Clip Raster by Mask Layer tool to clip your DEM to a vector polygon:
If this is the tool that you are trying to use already, then is there some kind of error that is being reported when you run the tool? Knowing what that is may help to diagnose the problem.