After searching for an answer and trying everything possible I have ran out of options but to ask it myself.
After following Android with Google+ Sign-in tutorial I ran into the most annoying and least descriptive error ever, the "An internal error occurred" on device. Nothing in the logs. The thing is, that after clicking the Sign-in button on virtual device I DO get prompted with permission requests, but running the same application on an actual device keeps throwing the error.
I did fill in the consent page, check the package names, create a new key and check package names and keys again and so on, nothing seems to work.
If anyone has had the same experience (working on AVD but not on actual device) please do throw anything at me, no matter how silly it might be.
Cheers!
P.S. Forgot the crucial part! If "addScope(Plus.SCOPE_PLUS_LOGIN)" is removed the application calls the onConnected method. So I guess I need an alternative for the same row that would keep the scope I need.