I think you have the same issue as this thread: [https://support.mozilla.org/questions/1025708 Black screen in firefox... now also no user profile]. Could you check that and see whether the solution there works for you? (By the way, the Old Firefox Data folder should be on your desktop from the Reset)

See also: *https://support.mozilla.org/kb/how-run-firefox-when-your-profile-missing-or-inacc This is usually caused by a problem with the profiles.ini file and the profile marked as Default=1 in this file is no longer present on the hard drive. *Windows: %AppData%\Mozilla\Firefox\<br>C:\Users\&lt;user&gt;\AppData\Roaming\Mozilla\Firefox\Profiles\&lt;profile&gt;\ *Linux: ~/.mozilla/firefox/ *Mac: ~/Library/Application Support/Firefox/ You can use one of these to make Firefox create/use a new default profile: *Delete the profiles.ini file to force Firefox to create a new default profile *Use the Profile Manager to create a new profile *Use "Choose Folder" when you create a new profile to select the location of a lost profile and recover this profile *http://kb.mozillazine.org/Profile_Manager *https://support.mozilla.org/kb/Managing+profiles *http://kb.mozillazine.org/Profile_folder_-_Firefox