your app mega 888 why not is not available?

That is not an Apple app. If you have questions, ask the app developer. They determine which app stores their apps are in. And if and when to remove them. How to contact an app developer - Apple Support

Hello.

First of all, we are not Apple. We are users, who ask questions and give answers just like you. As Lawrence said, some apps block VPN connections. Maybe disable your VPN then try it again. If that doesn’t work, contact the app developer.

I note that you are using VPN. Many apps block connections through VPN.