Refractivity coefficient: The input is not within the defined domain

Hi,

I've followed the steps in "Setting up the viewshed geoprocessing service (ArcGIS Pro).pdf".

But when I excute "ElevationTools.pyt" I get these errors:

```
Start Time: lunes, 18 de julio de 2022 19:56:07
Maximum distance: 15000 meters, DEM resolution: 90 meters, Mosaic Layer: C:\ElevationPro\Data\Elevation.gdb\dem90m, Observer offset: 1.75, Surface offset: 0.0.
Failed to execute. Parameters are not valid.
[ERROR 000864:](javascript:void(0);) Refractivity coefficient: The input is not within the defined domain.
[ERROR 000892:](javascript:void(0);) The numeric value is outside of the valid range.
Failed to execute (Visibility).
File "", line 729, in execute
File "", line 319, in executeVisibility
File "D:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\geoprocessing\_base.py", line 512, in
return lambda *args: val(*gp_fixargs(args, True))
arcgisscripting.ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000864: Refractivity coefficient: The input is not within the defined domain.
ERROR 000892: The numeric value is outside of the valid range.
Failed to execute (Visibility).
Failed to execute (Viewshed).
Failed at lunes, 18 de julio de 2022 19:56:13 (Elapsed Time: 5,48 seconds)
```


In addition to the previous error. I have this questions, Is it necessary an ArcGIS Image Server license to publish the viewshed script tool?