The message will be because the files required for the creation of the 3D DEM are missing, likely to be “surgef.exe", surgein.dta” or “surgein.HR”.
See our forum post 'If receive message "Could Not Interpolate Elevations" (viewtopic.php?p=1496#p1496)' for some advice that will also assist the received error, making the necessary changes for the actual missing file.
The IRRICAD Team