If you've gone through the time portal to the 1990s and checked out the link given and the 'help' there, perhaps you've encountered the problem where Word is dumb enough to false-positive a capitalised form of a word but too clever to allow you to add
it to your dictionary.
Simply drill down into the dictionary in your settings and manually type the word with the capitalisation that you require.
FWIW the tone on this thread is ridiculous (I'm talking to you Microsoft Very Piouses).
If you post the same solution you've pasted into every reply triggering the keyword filter you use to identify questions (we know you don't read them) and someone comes along saying that they've seen you post that 100 times elsewhere and it didn't help, you
have two options:
a) READ THE ACTUAL QUESTION AND RESPOND WITH YOUR OWN VERIFIED AND TESTED SOLUTION, NOT A LINK TO ONE OF YOUR CRONIES
b) UNMARK YOUR QUESTION AS THE ANSWER AND LEAVE THE THREAD.