The  system requirements of RivEX are:

RivEX is an ESRI AddIn for ArcGIS 10.7, it will not run in ArcGIS 10.6 or earlier!

You must be able to write to your C:\ drive.

RivEX was developed on a Windows Microsoft Operating System (10). It has been tested on a Windows 7/8.1 64bit.  Please be aware the Author cannot provide comprehensive support for the Windows 7 environment as he does not own a copy of this operating system.  The Author will endeavour to provide support for all platforms but will be unable to replicate issues specific to these platforms so support may be limited. 

RivEX does not require the expensive network extension to run.  It will run under the minimum standard ArcView or "Basic" license.

Some tools in RivEX connect directly to MS Excel to transfer data.  This requires you to have at least Microsoft Office XP installed.  RivEX uses automation to access the Excel code library installed by Office.

RivEX will process data which is in the format of Shapefile or a Geodatabase FeatureClass.  Polyline, PolylineM and PolylineZ data are all supported. RivEX is not designed to work with data in ArcServer\ArcSDE. If your data is in this format you will need to export it to a File GeoDatabase.

Changes to the underlying database engine of modern MS Office (version 2013+) means RivEX can fail to process data held in a Personal GeoDatabase. These low level errors are outside the control of the Author of RivEX. There is a simple solution, copy your river network into a File GeoDatabase and use it from there.

If you are running this tool with an ArcView or "Basic" license  you should be aware that you will not be able to stream order a Geodatabase FeatureClass that participates in a geometric network.  This is because your ArcGIS license does not allow you to alter the schema of such datasets.  This is not a limitation of the RivEX tool but your ArcGIS license.