Try this:
- Open the LW plug-in manager and remove the Maxwell plug-in.
- Open the menu editor and delete the empty Maxwell group which probably remained in the Render category (right-hand panel) after the plug-in is removed (you may not have this group at all, in which case just ignore this step).
- Go to the Lightwave installation directory, open the Plugins\Maxwell subdirectory, right click on maxwell.p and display its properties.
- Make sure the file is 2,174,976 bytes long and the "version" tab displays 2.0.7. If it doesn't match, download the installer again and re-install the plug-in. If you reinstall, uncheck "Attempt to install Layout buttons" when prompted, we will do this manually.
- Open the LW plug-in manager again and load the maxwell.p plug-in. It should say "18 plug-ins found in 1 file".
- Open the menu editor, right click the "render" category, choose "Import Branch" and point it to the MaxwellMenuBranch.cfg file in the Maxwell plug-in directory. This should create the Maxwell group again in the Render menu, with the following buttons: Render, Render Options, Maxwell Attribs., Export, Plug-in Options, Import Cameras, Toggle Sky.
This sequence of steps will make sure the plug-in is loaded and installed correctly. Please tell me if the problem persists even after doing this.