Can you open terminal and run '''''ps -fe | grep firefox''''' and see if it's running? see screenshot for example If it's running just kill the process and try again.

Hi Brenda, If you click the Firefox icon but no window opens, a simple first step is to restart your computer and then try again. If Firefox still does not start, hold down the Option key as you click on the Firefox icon, then choose Open. This will start Firefox in Troubleshoot Mode. If the problem does not occur in Troubleshoot Mode, then you can disable your extensions one-by-one until you find out which one is causing the problem. For more info, visit [[Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems]]. If the problem still occurs in Troubleshoot mode, it may be due to some corrupt data in your settings. Your Firefox settings and info are kept in a folder separate from the Firefox program, called your profile folder. Try creating a test profile, to see if the problem still occurs. See [[Managing profiles]]. If the problem goes away, you can then [[Recovering important data from an old profile|move your bookmarks and other important settings into the new profile]].