Client is not responding to my invoice, help me asap

Hi there,

I have submitted work successfully and client is not responding to release my invoice. He is taking too much time, that seems unprofessional and delay in payment. Though he was online after my messages, he ignored to see my messages and not responding.

https://www.peopleperhour.com/freelancer/mitul/ios-android-ibeacon-game-wo/1138884
***Puzzle game invoice.***