I hope this is the right translation: *[https://support.mozilla.org/de/kb/firefox-profil-fehlt-oder-unerreichbar]

^That is the German (de) article and not the Dutch (nl) article. See: *https://support.mozilla.org/nl/kb/how-run-firefox-when-profile-missing-inaccessible This is usually caused by a problem with the profiles.ini file. You can use one of these to make Firefox create a new default profile or reuse an existing profile: *Delete the profiles.ini file to force Firefox to create a new default profile *Use the Profile Manager to create a new profile<br />If you still have an existing profile then click "Choose Folder" in the PM and select the location of a lost profile and recover this profile. You should find the profiles.ini file in this hidden location: *Windows: %AppData%\Mozilla\Firefox\<br>*C:\Users\&lt;user&gt;\AppData\Roaming\Mozilla\Firefox\ *Mac: ~/Library/Application Support/Firefox/ *Linux: ~/.mozilla/firefox/ If clearing the profiles.ini file isn't working then also check the location of the cache files. *Windows: *C:\Users\&lt;user&gt;\AppData\Local\Mozilla\Firefox\Profiles\&lt;profile&gt;\ *Mac: ~/Library/Caches/Firefox/Profiles/ *Linux:~/.cache/mozilla/firefox/ ---- *http://kb.mozillazine.org/Profile_Manager *https://support.mozilla.org/kb/Managing+profiles *http://kb.mozillazine.org/Profile_folder_-_Firefox