: You must have both Spatial Analyst and 3D Analyst enabled.
Using HEC-GeoRAS for ArcGIS 10.8: Compatibility and Best Practices hec georas for arcgis 10.8
Technically, official support from the USACE Hydrologic Engineering Center (HEC) for GeoRAS ended after version 10.2. However, later versions have been made available via the Esri FTP site to support subsequent ArcGIS Desktop releases: : You must have both Spatial Analyst and 3D Analyst enabled