Facebook instant games api method canSubscribeBotAsync method is not a function - facebook

Question

So my game wants the players to have the ability to subscribe to a game bot and I'm using FBInstant.player.canSubscribeBotAsync() method. But everytime, it will return an error that state
Uncaught TypeError: FBInstant.player.canSubscribeBotAsync is not a function
here is my code
FBInstant.player.canSubscribeBotAsync().then(function(yes){
if(yes){
FBInstant.player.subscribeBotAsync().then(function(){
console.log('sub');
}).catch(function(e)){}
}
});
I tried using this code from FB developer doc
FBInstant.player.canSubscribeBotAsync().then(
can_subscribe => console.log(can_subscribe)
);
but the result still the same.

Answer 1

It seems that I tried to let the player subscribe when they click the button and this error appears.
But when I switch it from letting the player click the subscribe button to asked when player finished loading the game, the error disappears. The program's flow look like this
window.onload = async () => {
FBInstant.initializeAsync().then(()=>{
FBInstant.startGameAsync().then((res)=>{
FBInstant.player.canSubscribeBotAsync().then((canSub)=>{
//Ask for sub or something
}).catch(()=>console.log("Error"))
})
})
But for me, this is a temporary fix since normally you should be able to call a function anywhere you want (working or not isn't my problem) and my problem is that I can only call FBInstant.player.canSubscribeBotAsync() inside FBInstant.initializeAsync() or FBInstant.startGameAsync() but not outside of them