see this article https://support.mozilla.org/ar/kb/how-do-i-use-firefox-spell-checker

Do you have a dictionary installed and selected?

You can see which dictionary is selected if you right-click in a text area and open the Languages sub menu. 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.

The spelling checker is enabled if [X] "Check Spelling" in the right-click context menu has a checkmark.

You can enable or disable spell checking globally:

• Options/Preferences -> General: Browsing: "Check my spelling as I type"

You can look here for dictionaries:

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

Note that you need a dictionary and not a language pack that provides string translations for the user interface.

You can check the layout.spellcheckDefault pref on the about:config page.

• http://kb.mozillazine.org/layout.spellcheckDefault

Don't ask me why,but I closed FF and when I reopened it,the problem was gone. I have always had spell check turned on,and have used the English dictionary forever. I appreciate you taking the time to consider my problem,however!