more than 30 day overdue on multiple payment applications.
First, if you're still within 45 days of when you first started work on the project, you should serve a notice to owner. You also should contact an attorney. You may have remedies under your sub-subcontractor agreement to help you get paid faster.
Send a notice to owner. Wait 30 days. If still not paid, file a lien (but file within 90 days of your last work).