This is no new phenomenon and most experienced Android users have surely been annoyed by this problem at one point of time or another: today we are talking about error code 912, the dreaded complication which renders app update installs from Google Play impossible. Thankfully, there’s a solution.
Depending on the frequency at which the error code appears on your afflicted smartphone, it might suffice to simply empty the cache of the Google Play Store app. In order to do this, you simply open your Android settings, go to the ''Apps'' or ''Application Manager'' selection, depending on which UI you have, swipe over the ''All'' apps and find the Google Play store app (it’s listed alphabetically) and tap on it. In its ''App info'' page, simply choose ''Clear Cache''. Done. In most cases, this should relieve you of the 912 syndrome without so much as needing to reboot your phone.
If this problem persists however, you might need to delete the data from the Play Store. By doing this, you will lose all of your chosen settings for the app and you’ll have to re-configure it to your liking afterwards.
That was it for the best case scenario. If this still doesn’t do the trick, you might need to take more drastic measures. Go back into your system settings, choose ''Account'' and then ''Google''. Select your Google account and tap on the menu button on the top right corner of the page and select ‘Remove account’ if you have stock Android, or choose the ''remove account'' button on TouchWiz. Then, go back to accounts. Now you will need to add the account again and sync it with your smartphone. This should have you saying goodbye to Error Code 921 once and for all.
Did you try any of these methods? Which one worked for you?