Solution: Remove and add new Google account
Go to Settings > Account & sync > Google > Remove account
Remove Google account
Then go to Settings > Apps> All
Select All apps in Settings
Select Force Stop, Clear Data and Clear Cache of Google Play Store, Google Service Framework and Download Manager
Force stop, clear data and clear cache apps
Restart your device
Restart devices
Go to Settings > Google > Add accounts
Add new Google account
Go to Google Play Store to download or update your apps
Restart devices and try to update apps
Above are instructions of how to fix error 491 in Play Store. Hopefully this information is useful to you. And if you want to know more about the way to fix errors on Google, please visit us at our homepage Google Play Store Free App. Good luck and thanks for reading!