Hello Ian,
Most probably, this is an issue related to permissions.
After the installation process completes, can you please try running the Web Part Registration Wizard from the Start menu >> All Programs >> Nevron SharePoint Vision
Please, let us know if you can see a list with your web applications?
If the Nevron assemblies are not in the GAC, you can drag and drop them from the Nevron installation Bin folder.
Best Regards,
Nevron Support Team