Hello Peter,

Thanks for your feedback. Could you precise how you used the extension step-by-step?

The recommended happy path is the following:
- Download the extension
- Click on "Extensions" on Firefox toolbar
- Pin "Fullwidth messaging LinkedIn" extension to the toolbar
- Clicking on "Fullwidth messaging LinkedIn" icon in the toolbar opens the extension popup
- From the popup, you can navigate to LinkedIn messaging and switch it to full width

I'm here to help if you are still experiencing issues after reproducing these steps. In the meantime, I will add this step-by-step guide to the extension page.