That happens occasionally.
It may be that a portion of FF is already running, thus preventing a new window from opening.
Right-click on the START Tool Bar and select Task Manager.
In Task Manager, select the Process tab. Click on Image Name to alphabetize. So down the list to see if firefox.exe is listed. If so, select firefox.exe and then select End Process.
After a few moments, try to load Firefox.
If it still won’t load, you may need to uninstall and reinstall Firefox.
Thanks, but I have already encountered that one - that’s not the problem this time.
Thanks, but I have already encountered that one - that’s not the problem this time.