I suggest you try a different dictionary. Someone may have added all your
misspelled words to the main dictionary. Other than that, I would reinstall
Excel.
Give us and example of a word it does not find. Where is the misspelling -
in a cell, in a comment, Word Art, a text box, an AutoShape, SmartArt, on a
chart?
You might check to see if you are using the correct language setting for the
dictionary.