I have been looking for a solution for this since quite a while. But I am not able to find anything. I have implemented Push Notifications for iOS using FCM. But I don't know if FCM supports iOS 10 rich notifications. If it does, I didn't find code to implement it. Thanks in advance.
I have the same question why rich notification not working.. and the problem is with FCM mutable-content payload .. it turns in to gcm.notification.mutable-content when payload receives and that's why there is a problem which is not resolved yet.
For more information, you can check this issue from github.
Its resolved now.. you can check that link and also check this answer AL.