This client is very slow to pay and difficult to contact.
You really need to retain a construction attorney to evaluate your situation and to provide advice.
You don't provide enough information to be able to evaluate your claim, and do not specify what type of project is at issue, who you contracted with, and who the owner is. The legal analysis and indeed the controlling law can change based on the actual situation.
Good luck.
Must send timely notice of unpaid billing before then you can send notice of claim on bond.
Most people send the notice of unpaid bill and claim on bond at the same time.