Hi Cassie
I know from your email to support that you’ve got this sorted now but in case others have the same issue, here’s how to resolve it.
If you don’t see an Extensions menu, or there is no Shaderlight for SketchUp item under it, you will need to tell SketchUp to allow unrestricted access for extensions. You can do this by choosing the Window -> Extension Manager menu option, clicking the cog icon in the top-right corner of the Extension Manager window and then selecting ‘Unrestricted’ in the Settings dialog that appears.
Thanks!