Try:

1. add your formatted AutoCorrect entry,
2. open the normal.dotm file directly (How to Open the Normal Template),
3. try using your AutoCorrect in the normal file,
4. undo the text you just inserted,
5. dirty the page by typing something and then backspacing to delete it (not Undo),
6. save and close normal.dotm.

Make a backup first. You do not want any text on the page in your normal.dotm.