System: MacBook Pro (Retina early 2015) @2,7GHz i5 OS: macOS High Sierra 10.13.6 Today after trying to open a random website out of my Mail-App, Firefox did't open. Now, when launching the Firefox-icon in the dock, it does the little jumping-animation, but after that nothing happens. No error-message either. Before that, Firefox functioned perfectly. I can't remember installing any updates or changing any preferences today. I tried reinstalling Firefox (clean reinstall) as described in several other posts. Also tried the suggestions on the Mozilla Support-Page ("Firefox won't start - find solutions"). Opening Firefox in Safe Mode or by holding the option-key also didn't work. Would really appreciate your help, thanks. Edit: When moving and launching Firefox from another drive (SD-Card or initial "virtual" Firefox-drive) it somehow workes!