Unpaid Invoice for more than 15 + 24HRs

Hello, I worked with a buyer on a Javafx bowling game simulation software. Last time i raised invoice and remained unpaid for 15 days then after was paid [I dont know if PPH paid the invoice Or Its him].

He contacted me on 13th August, 2020 that i should continue working on the project that could add me a little more. I finished the work in less than 24Hrs as he requested but now am having trouble getting my invoice paid. The problem is that he is not communicating to me. I need this money. The invoice is due and 15 days have passed. 

Please assist