Is it possible that Firefox performed a "reset" during your installation? In that case, you should find a new "Old Firefox Data" folder on the desktop. Can you find that?

Similar threads from when Firefox 29 was released:

• I had Zotero connect to this with my older Version, it automaticlly upgraded and now I seem to have lost it, how do I get it back?

• Where did zotero go?

Do you have all these dictionaries installed and at least one selected?

You can see which dictionary is selected if you right-click in a text area and open the Languages submenu. At least one dictionary should be installed and have a check mark to indicate that it is selected.

• Open the "Add Dictionaries" link to install a dictionary if you do not have one.
• Make sure that [X] "Check Spelling" in the right-click context menu is check-marked.

You can enable or disable spell checking globally:

• Firefox > Preferences > Advanced : General: Browsing: "Check my spelling as I type"

You can look here for dictionaries:

• https://addons.mozilla.org/firefox/language-tools/

Yes there us a new "Old Firefox Data" folder on the desktop, but what do I do with it ?

I did all you describe to add dictionnaries and they were added and indicated as "active". But when I write a text and right click to choose the language there's only one dictionnary, the French one.

The dictionnaries are installed and active, but when I right click they don't appear.

It is possible that there is a problem with the file(s) that store the extensions registry.

Delete the extensions.* files (e.g. extensions.json, extensions.sqlite, extensions.ini) and compatibility.ini in the Firefox profile folder to reset the extensions registry.

• https://support.mozilla.org/kb/Profiles

New files will be created when required.

See "Corrupt extension files":

• http://kb.mozillazine.org/Unable_to_install_themes_or_extensions
• https://support.mozilla.org/kb/Unable+to+install+add-ons

If you see disabled or not compatible extensions in "Firefox/Tools > Add-ons > Extensions" then click the Tools button at the left end of the Search bar to check if there is a compatibility update available.

If this hasn't helped then also delete possible addons.json and addons.sqlite files.

You can also check for problems with preferences and rename (or delete) the prefs.js and the user,js file when present to reset all prefs to the default value.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

You can use this button to go to the currently used Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)