Send invite to facebook friends to try out a game

So I want to add a feature in my game where you can send your Facebook friends an invite for it. I've integrated the sdk and everything, my confusion is about which function to use and how ? I understand FB.Mobile.AppInvite is deprecated? I'm using FB.AppRequest and I did manage to get the send invite option in the game but the people I sent the request to didn't receive it.

I'm also not clear about all the parameters in there. Should I just send the message + link in the message parameter? What is the callback parameter for and what goes there? How do I know if someone's invite was opened so I can reward them? Really confused about all this stuff, and any help would be greatly appreciated. Thanks!

 

I seem to remember that FB changed these invites a while back so that people don't see them as often. (Or at all?) Also, I found this.

https://stackoverflow.com/questions/47263438/fb-apprequest-does-not-work