I fixed this by passing the redirect url to the FacebookRedirectLoginHelper::getAccessToken()
in my callback function:
Changing from
try {
$accessToken = $helper->getAccessToken();
}
...
to
try {
$accessToken = $helper->getAccessToken($fbRedirectUrl);
}
...
I am developing on a vagrant box, and it seems FacebookRedirectLoginHelper::getCurrentUrl()
had issues generating a valid url.