If you miss out on something that would be enjoyable or useful to you, you are not involved in it or do not take part in it. We're missing out on a tremendous opportunity Well, I'm glad you could make it. I didn't want you to miss out. = lose out
If you miss out something or someone, you fail to include them. There should be an apostrophe here, and look, you've missed out the word `men' altogether! What about Sally? You've missed her out. = leave out