RenderMan for Houdini v23 on Windows now requires an additional line in the configuration file in order to load the plugin correctly:

PATH=$RMANTREE\bin;&

• RenderMan for Houdini version 23 v23 currently only provides support for the following Houdini versions:
  • 17.0.56506
  • 17.5.360
  • 18.0.268 (beta)
• Rendering with RenderMan will not operate on Houdini Apprentice editions, see Side FX's website for options that allow Third Party Rendering
• Houdini Indie is only compatible with 17.5, you must be using at least version 17.5.210 or higher