If the license requirement is only for revenue, then it is irrelevant in a negligence case. For example, if a person involves in a car accident, the fact he does not have a driver's license does not mean he is negligence per se.
In your case, I assumed you wanted to sue under misrepresentation or fraud. Those are intentional torts so that with or without the license is a non-issue.
I would read the contract carefully and find out whether there is a ground to sue for breach of contract. Misrepresentation and/or fraud is difficult because you have the burden to prove intent, that the guy intended to defraud you.