This is a problem common problem for some people.The short answer is you won't level up because you've missed an ingame trigger.

I've played the story mode through,deliberatly keeping the money side tight,getting just enough to activate the missions.
At the end of the cut scenes when your left on manhatten you should be about LEVEL 23 & have a net worth of around $400,000.
I've also done it being as greedy as hell and ignoring Juni for hours on end.

Your best bet is to go back to an old save and see if you can find what you missed.

Its a corrupted savegame. At the end of my main story I was level 32 because I had like a worth of 2 mil. or something. Also, the after-story leveling system is very diffrent. Rather than show the amount $$$ you need to reach to level, it shows how much cash you still have left before you level, but from what I've heard of your case, its a bug or corrupt save file.

There can be problems, if your are not physically where you should be to trigger points to continue. I have done it several times and had to back up and replay a level.

It's amazing what a week of modding can do for your understanding of how a game works,my finish level in the above post is a little high.

I've checked through all of my old save games(I have 3 different sets)and they all say the same thing for the levels.When your on the Osiris for the last time,just before going to fight the nomads in the final battle,your at level 17 with next level requirement as mission.

If you are playing the story mode it doesn't matter how much money you go and get because the levels are preset in the game.This means that if you were to finish the pittsburgh mission you will be level 2,you then go and earn 100 million you will still only be level 3.The game deliberatly blocks you from leveling up.

Andkat you finished on level 32,that is because after the story the game looks at how much you have,checks it's level requirements and ups your level to suit.

Which is why you should do 100s pf misions during the main story. Oh, and find numerous powrful weapons (including class 10). And destroy 1000s of ships. It really really benfits you in the long run.