Your post here is a bit scant in details, I think. But here’s my understanding if I’m incorrect.
You purchased something from a seller (naming the seller is against the rules of the forum, so I’m just gonna call this person “seller123”). Seller123 was supposed to make your Boxing Ring Chess App; you paid part up front and when they didn’t deliver, you paid the second part – as per your agreement. Now, Seller123 hasn’t delivered anything and your $3300 is gone.
For this to have happened, there must have been an order (purchased a gig) and that order must have been marked as delivered – either by you personally or by the system auto-completing a delivery if you didn’t respond within 72 hours of the delivery.
Well, if you made that agreement on Fiverr, you can contact Customer Support and tell them exactly what happened. If you ordered a gig from Seller123 and nothing was delivered or that which was delivered was not up-to-par, then Fiverr’s dispute system can help return your money as Fiverr credit! You’ll be given all but your processing fees back as credit that can be spent on Fiverr. Again, just submit a ticket to Customer Support and make your case: explain what happened, attach screenshots of the conversation that prove you’re in the right, and ask for help in resolving this issue.
Maybe there’s more to this story that you’ve not stated, so perhaps this won’t work. BUT, it is the best course of action to getting what you want.
If you did not make an order through Fiverr and instead paid in another way, you’re screwed and no one can help you. Fiverr is here as the middleman who protects buyers from this happening, and if you circumvented Fiverr then you circumvented that protection.