To fix Gmail promotions tab not working, you are expected to follow and apply few more instructions. Like, firstly be sure that you are using the latest version of the Gmail app. Now, you can try to view on another device. Now, you can also try to use a different tablet. Now, you are expected to refresh the Gmail app just by pulling down the Gmail promotions tab screen. After that, you should try to restart the device. Once you do follow and apply the steps, you would be able to resolve and troubleshoot the issues without any fuss.