Contact your state Department of Labor to file a wage complaint. Non-payment or late payment of wages are something the DOL does not have any patience with. As in once you file a complaint showing the hours worked and that you weren't paid, they will give your employer the option of paying you immediately or being shutdown and locked out until all back wages are paid. Additionally, any adverse action against you by your company (extortion, termination, coercion, etc) after that complaint is something the DOL takes about as well as a defendant flipping off a judge in court.

Largely this is because employee wages have first claim on a company's assets when settling liabilities. If the DOL has to force your employer into bankruptcy to pay wages immediately, tough shit for your employer. Which gives your employer a very strong incentive to cooperate promptly.

Get an employment lawyer, you can probably run them through the cleaners if they're refusing to pay you or withholding owed pay for a significant period of time.

Check your state laws. In California an employer has to pay you within ten days of the end of the pay period. They owe you a full day's wages for every day they're late, which you can collect in small claims. If they pay you with a check that bounces they owe you that PLUS triple the amount of the check.

If you're a contractor and not an employee, things are different. The governing law is whatever your contract with them calls for. If they fail to honor the contract you can take legal action for breech. If you work for a company that has the contract, the company still has to pay you. Not getting paid by the client is not an excuse. In that case you would sue your employer, not the client.

I worked for a contractor that shorted me $5 every week.