У вашего броузера проблема в совместимости с HTML5
Getting "Gmail App Waiting for Sync" try to solve that by following steps shown in the tutorial video which may fix the waiting for sync error in the gmail app 2019.
1)Check your internet connection
2)make sure your Auto Sync Gmail option is turned on
3)If still waiting for sync persists try to restart your mobile and try clearing data and check.
4)on your phone settings app,check for user account and check auto sync is on for google accounts.