If you are dealing with the issue of Gmail forwarding not working then you need to remove the Google account. You can give the Gmail application a complete account restart. The simplest way to do so it to remove the Google account and re-add it again. To remove Google account on your Android devices, start by opening the settings app and choose password and accounts. Here, find the Google account that you want to remove and then click on it. Lastly, click to remove account and then follow the on-screen instructions properly. Follow the steps properly so that you can start using Gmail application again.