i also had this issue and followed every solution to try and restore them. nothing worked. Then I re-downloaded the firefox app for desktop and when I restarted it and logged in, i went to bookmarks, bookmarks toolbar and they were all there. I had to turn the bookmarks toolbar from never show, to always show... (which didnt work previously) and it was fixed. It only took several days of giving up, then 3 + hours tonight until 1am and not giving up, to finally figure it out.