Facebook forceDialogAuth

I've got the below code, it currently works as is.

However if i change the fb.forceDialogAuth to false, the a message does come up saying "This app wants to access your profile etc" but I press OK and then nothing happens. Once I change it back to false and enter the details it seems to work fine

Any ideas what I'm doing wrong?

btnFacebook.addEventListener('click', function (e) {
       fb.appid =  XXXXXXXX
       fb.permissions =  ['read_stream', 'email']
       fb.forceDialogAuth = true
       fb.authorize();
});
 
    fb.addEventListener('login', function (e) {
        if (e.success) {
            LoginWithFB();
        } else if (e.error) {
            alert(e.error);
        } else if (e.cancelled) {
            alert("Canceled");
        }
    });