7 Best Ways to Fix Gmail Waiting for Sync Error
Before you begin, I guess you have already checked your Internet connection (mobile and Wi-Fi), that the airplane mode is off and your phone has restarted. If you get this error in a browser, try the mobile app instead.
Let's start.
1. Gmail is down
It would not be the first time either. Open Downdetector and check if Gmail is down. Especially in your part of the world. Downdetector monitors several services and indicates whether they are operational or not.
Useful site that you should consider to bookmark. If the Gmail servers are down or have problems, you can not do much. Take a short break. Maybe go for a walk.
2. Update the application
You should always use the latest version of all applications because they come with new features and bugfixes. Check if an update is available on the Play or on the App Store. You may also consider updating your operating system. It could help.