It's been more than 24 hours since my map has been pending public. Anybody know why?

All maps are reviewed by humans before going public. Humans are, of course, fallible. The 24 hour thing is really there to give you an idea of how long it might be; but really, it could be any length of time. For example, Not A Soul was only pending public for 2 hours. Whereas I've had maps pending for 4+ days. It all depends on when someone reviews it.
It also could be delayed because there's an issue with the map that keeps it from being published. You should get an email, but not always. Go into the map editor, and if there's something wrong, it'll tell you what it is so you can fix it. If not, you'll just have to continue waiting.

Edited 5/13/2017 00:30:59

Actually, if there is something wrong, it won't let you change its mode to public

Edited 5/13/2017 07:39:19

That's only if WL can detect the issue. Sometimes you can set it to public, but in the review, someone notices something wrong with it (missing connection, extra connection, etcetera) and they send it back to you for fixing. That's why they have humans review it in the first place rather than WL automatically publishing them--because human eyes can see problems that WL can't. So really, it all depends on what the actual problem is.

Correct, but if that's the case, why would you advise him to go the map editor, so it will tell him what is wrong? If the map editor knows something is wrong, it will not let him publish it.

Go into the map editor, and if there's something wrong, it'll tell you what it is so you can fix it. If not, you'll just have to continue waiting.

Fizzer will leave a message that shows up when you reenter the map editor.

Edited 5/13/2017 10:09:17

I did the validation. So far I have not gotten an email about it except for the one saying it is in public pending.

Validation doesn't help in this case. I'm talking about a problem that SO can't detect; so Fizzer sends it back to you with a message.
If there isn't an issue, then it's just a matter of waiting. As I said, I've waited 4+ days before. A few months ago, there was a holdup that caused several maps to be held back from being published for about 10 days. So just give it some time.

Still not published......

Did you check the map editor?
Regardless, whether you did or not--we've given all the information we can, we can't help you anymore. And posting to the forums isn't going to get it published any quicker. Go to the map editor to make sure there's nothing wrong with it; and if there's not, then just wait. Whether it takes 3 days or 3 weeks, it will be published eventually.