Dynamic-Loading:
Several of Fredo's tools are construed in such a way that if you install them using the AutoInstall feature [OR even manually install from an RBZ archive] then you will need to restart SketchUp to see the changes that they bring...
Most plugins can be 'dynamically-loaded', and these will give their new functionality immediately they are loaded, but some - like Fredo's - do require a restart 😞
Permissions:
The AutoInstaller will have checked if there are permission issues, but some subtle limitations might still escape this checking... so it's always best to manually check and ensure that you have given FULL security-permissions to the Plugins folder for ALL users: especially, immediately after you make a new installation of SketchUp - when Windows has a nasty habit of initially limiting security-access to any new 'Program Files' folders/subfolders to protect you from yourself !! ... 😒