Update server not available (error: 12)
This is one of the most annoying problems I have got with Google Chrome browser until I finally figure out the cause.
It is many time when I Chrome reported it had failed to update to latest version. Even when I manually updated it, it seemed to be in good shape for a while before it became non-updateable again. The general error message led me to many posts/questions across the Internet but almost nothing helped. Eventually, when I read a post saying something about missing language files, I realized that I have been using CleanMyMac to strip out some of the languages that I never use in both OS X and application I installed.
I decided to manually update Google Chrome and not to touch its language files again. The great thing comes! I have never encountered the error ever since!
So, if you are using any kind of applications to remove unused language files (I know another app call Monolingual) from your apps, please remember to leave Google Chrome alone! Otherwise, you might not be updated to its latest version any longer.
I found that it is a bit hard to figure out this problem initially, so I would like to share the information here for those who have not resolved it yet.