see https://support.mozilla.com/en-US/questions/850263

I solved it by opening my views, and clicking next to "navigation Toolbar"

Again, I solved it myself by doing something with the ctrl button according to firefox troubleshooting, and also using "views" and clicking on navigation toolbar.

I notice that my answer on the referred to page is the solution that you found yourself. Everyone has to ultimately solve their own problems. Would you mark the problem as solved on your original post, so that it helps others. You do that by clicking on solved next to the best answer.