Hangouts Google Play Services problem Everytime I update hangouts I get this message whenever I open the app: "unkown issue with google play services". What is the cause of this problem? And how to solve it?
This problem can be caused by a old version of play services.

To update the version manually open this link on your android device and click update if there is an update.

Hope this solves your problem

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EDIT:

Hope this way works for you. Keep in mind that setting names can be different from brand to brand. 


Go to Setting > Security > Device Administrators
Un-check Android Device Manager
Go to apps and uninstall updates to Google Play Services
Go to Hangouts, it should show a message saying that you need to 'update Google Play Services'. Click update.
After updating, Hangouts should not show the error message
Go back to Settings > Administrators and check Android Device Manager