Hello Guidobert. 1 - With firefox loaded, open a new tab, and type '''about:config''' in the address bar and press enter. Then click on the button accepting the risk to proceed. 2 - In the search bar on top of the page that has been loaded, type '''demand'''. 3 - Make sure that the '''browser.sessionstore.restore_pinned_tabs_on_demand''' option has been marked as '''true''', and if its not, then just double click on it. 4 - Restart firefox. This should fix the issue.