Here is the plugin: https://www.spigotmc.org/resources/megaarena-classes-tournaments-perfect-epc-1-7-10-1-9.35951/ Please help
You can't buy that plugin. It was put on InactiveResource because it was inactive. You cannot buy that plugin any more unless the author becomes active again and reports it.
The author of the resource requested that it be deleted just over a week ago. Not much you can do about that, unfortunately. You're not always guaranteed that a resource is going to function as intended, nor that you will always have access to it, because authors may either request deletion or become inactive
So, do you expect your car mechanic to fix your car if you just say "Oh hey, my car isn't car'ing anymore"