To fix Gmail forwarding not working, you are supposed to go back to the settings page for the Gmail account that you wish to forward messages from. Then, you must refresh the browser and after that, you are expected to click the forwarding and POP/IMAP tab and then in the forwarding section, you are supposed to select forward a copy of incoming mail to and then you are expected to choose what you want do. Apply the steps one by one and so you will be able to resolve and troubleshoot the issues without any fuss or chaos.