I let my studies suffer to build a CRM for a company only for them to say they have no money to pay me. I feel like a failure. That was my first ever successful project.

Fuck them. It's an accomplishment even if they are dicks, you should be proud of yourself.

You didn’t give it to them right? And how much did you charge? Ask for an upfront next time

Welcome.

For the future:
1) set up a contract, covering scope, delivery time as well as "waranty" (in how long you'll fix bugs for free)
2) have them sign it
3) if a design is involved, have them sign it
4) if they have changes, let them know, they are not within the scope of the project and that it will take longer (at least have them aknoedge this in written form). If it's something big, also estimate how much longer/how much more money it will take.
5) have them pay 25-50% upfront (with a clause in the contract, that they get there money back if you don't deliver)

People will try to fuck you over and take advantage of you. Don't let them!

In this case, if you have anything in writing, insist on that money. Send them a bill and if they don't pay, go through the appropriate channels if you feel comfirtable escalating it.
Also if they don't pay, don't give them any code. If you allready have and still have access to the server, delete the code there (but keep a copy in case they do pay). Also opensource it, as an "advertisment" for yourself. List it in your portfolio.

This certainly proprietary to you, no court l will award the IP to them on a failed contract, I don't know where in the world you are, but in the UK for example, verbal agreements are in fact also contracts as long as there is a sufficient evidence on the balance of probability.

It is software, it has value, if they want it, they must back up it's value somehow, otherwise they can't have it, ask them to register you as a shareholder or something instead, get like X % of the company if it suits you, but they either pay up or don't have it, simple as that.

another day, another Win 10 won't play audio through headphones again... :(