I had an agreement with a client to work full time with them for two months at a set hourly rate, and to send an invoice to them every month. For the first month, I sent the invoice and was paid after 8 days. The second month, I've sent the invoice and after a week the company contacted me and said I did not fill out my hours properly (I fill out my hours on a shared google sheets file) and so I made the necessary changes, and sent it to them. A week went by and they have not responded, I have sent emails to a few different people (product manager, and both cofounders) in the company but have not heard anything back.
What is the appropriate thing to do from here? In the contract we did not specify a due date for payment of invoices. How should I proceed?
Edit: I am located in nyc, so is the company.