There are many factors that need to be considered before a successful remedy;
What remedies are stated in your contract with the Prime?
Some Primes & Owners require specific invoicing formats. Did you follow their format correctly?
Did the quality of your work meet the Contract specifications?]
Is the work gig free after inspection?
Was satisfactory paperwork submitted?
Was everything on time?
Does the Prime have a history of non-pay?
That said, your opinions may be limited. Small claims court may be an option if the amount is small enough. If it is a large amount, you could hire a lawyer. Mediation is another option but it also involves lawyers.
