FAILED TO INSTALL PAY PER VIEW

Hi Friends, i recently bought the pay per view plugin, installed it on Rutakirwa. com, but its not working on the final product, it brings this message

"There was a problem connecting to PayPal to setup your purchase. Please try again.

10002 – Security error – Security header is not valid"

What next, can you forward me a step by step guide on how to deal with this; install plugin, activate the login methods, as well as linking pay pal?

Thank you, and please help