I've installed a new 27" iMac (2017) running the High Sierra OS. The installation used Time Machine to transfer two user accounts and the applications from my previous system, which ran Firefox without a problem. This new implementation of Firefox on the 27" iMac was highly dysfunctional and would not allow me to bookmark new pages and would not sync with bookmarks from my Macbook Air. Consequently, I deleted Firefox from my new system and downloaded and installed a new version of Firefox. With the new version of Firefox I still have problems bookmarking pages, I can't sync with my MacBook Air, and I can't import the bookmarks from my Macbook Air. When I attempt to import bookmarks I get the following notice - "Unable to process the backup file."