Google Hangouts 4.0 is the latest iteration of Google's messenger app but you might want to hold off updating to it if you haven't already. Users have reported a glitch in Hangouts 4.0 is preventing them from using the app under certain conditions.
Hangouts 4.0 sports a new simplified design and improved speed. As the app can consolidate multiple accounts, many users go through Hangouts for instant messaging and SMSing for work and play.
The glitch, first reported by Android Police, won't let you use Google Hangouts unless it can sign into all accounts linked to the app, even if it's not technically possible. So if your work Gmail or Google Apps account doesn't allow you to use Hangouts, the glitch will prevent the app from working. This is a problem that has been reported by a number of users since the app was launched last month.
The most obvious solution to this issue is to downgrde to Hangouts 3.3. You can also remove the blocked Google Apps account. If you have admin access to the Google Apps account in question, you can try activating Hangouts for it to remedy the problem.
[Via Android Police]