◦ Go to ~/Library/Application Support/Firefox/Profiles/ (you can access this by opening Finder, clicking "Go" in the menu, and selecting "Go to Folder"). 
◦ Find the folder that ends with .default and look for a file named prefs.js. You can move this file to your desktop (as a backup) and then try opening Firefox again. 

1. Restart Your Computer: Sometimes, a simple restart can resolve issues with applications that are not responding. 2. Check Activity Monitor: Open Activity Monitor (found in Applications > Utilities) and look for any instances of Firefox that may be running. If you see any, select them and click the "X" button to force quit. 3. Safe Mode: Try starting your Mac in Safe Mode. To do this, restart your Mac and hold down the Shift key immediately after you hear the startup sound. This will load only essential system software. Once in Safe Mode, try opening Firefox. 4. Create a New User Account: Create a new user account on your Mac to see if the issue is specific to your current user profile. Go to System Preferences > Users & Groups, and create a new account. Log into that account and try opening Firefox. 5. Check for Updates: Make sure your macOS and Firefox are both up to date. Sometimes, compatibility issues can arise from outdated software. 6. Remove Firefox Preferences: Corrupted preference files can cause issues. You can try removing the Firefox preferences: ◦ Go to ~/Library/Application Support/Firefox/Profiles/ (you can access this by opening Finder, clicking "Go" in the menu, and selecting "Go to Folder"). ◦ Find the folder that ends with .default and look for a file named prefs.js. You can move this file to your desktop (as a backup) and then try opening Firefox again. 7. Check Console for Errors: Open the Console app (found in Applications > Utilities) and look for any error messages related to Firefox when you try to open it. This might give you clues about what's going wrong. 8. Reinstall Firefox: If you haven't already, completely uninstall Firefox by dragging it from the Applications folder to the Trash. Then, download the latest version from the official Firefox website and reinstall it. 9. Check for Conflicting Software: Sometimes, other software can interfere with Firefox. If you have any third-party security software or VPNs, try disabling them temporarily to see if that resolves the issue. 10. Contact Mozilla Support: If none of the above steps work, consider reaching out to Mozilla support for further assistance.