Facebook Friends can't accept my game invitation with error 405: http verb used to access this page is not allowed

I have created a game in unity that integrate Facebook, so a list of friends appear so you can invite them to play the game, when I invite a friend, a notification appear on his notifications (only if he is a tester, because my app still in testing mode), so if he click the notification, the game should start on the browser, but an error is displayed instead. any one can help ? my game is created in unity 5.6 using WebGL and I am hosting it on my web server (on amazon web services)

Are you sure you have placed the correct URL in the field for Canvas Implementation of your game ?