ArcGIS Pro 2.4 registry key is now located at HKEY_CURRENT_USER\Software\ESRI\ArcGISPro. To resolve this ArcHydro Pro installation problem temporarily and at your own risk, create a dummy string value (say 2.4) for the RealVersion key at HKEY_LOCAL_MACHINE\SOFTWARE\ESRI\ArcGISPro.
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