Buyer's cancel the order after a month

[pro_hussain]

Hello guy's last month I deliver the order to my client and fulfill all requirements we discuss in pre order chat.
after a week he back with a new issue in app. i ask him to pay extra and we create a second new  order for this issue, he was ready to create 2nd order at that time  but after discussing budget he refused and wanted to solve problem free. The problem is totally new and not link with previous order tasks.
Unfortunately I was not able to solve second order issue due to my commitment with other clients project.
Today after a month the client cancel the first order.

My only fault is i can't see fiverr support email on time. Now i request fiverr support team to review our order chat and after order chat in inbox. also attached some screenshots to prove my side. Guy's can you please suggest me what will I do in this case and in future to prevent from this type scam