You wrote that you "joined" the company, not clear what relationship you had.
If you got hired as a W-2 employee (usually called full-time) you should contact the California Labor Commissioner's Office. Employers must pay wages in a timely manner, and they must also pay their portion of your tax withholding. By law, so the state has enforcement procedures.
If you got hired as a contractor/freelancer/1099 then you will have to file a lawsuit for breach of contract. You can hire an attorney if you think you need to. You will need to get the contract and all evidence of work you did and payments received (emails, etc.). Such cases usually go to mandatory arbitration, the process can take a long time. Depending on the amount and some other details you may be able to sue in small claims court. Keep in mind that if you win your case you will just have a judgment, not payment, and enforcing the judgment can take a long time and more legal fees. If the company doesn't have the money you probably won't get anything no matter what.
In the meantime I suggest you stop delivering anything to the employer/client and find work that pays. And try not to put yourself in the position of an employer or client owing you a lot of money, or you owing them a lot of work.