I created an account just to reply here with what worked for me in case others are still having issues. Hopefully this helps some of you. Using my iPhone I went to Settings > Apple ID > Password & Security. From there I selected Apps Using Apple ID. Scrolled down to the app I was having issues with and clicked on it. Selected Manage Settings Scrolled down new list and selected app again. Disabled the Forward To option by moving the slider to the left then backed out so that it saved the choice. Went back to it and re-enabled the Forward To option by moving the slider back to the right. Doing this was essentially a reset for the forwarding function for that app and I immediately started receiving forwarded emails. Not emails that were previously sent, mind you, but all new emails moving forward. I hope this helps some folks because I know how frustrating it was for me.