Is it possible to connect existing LT account with my Google or Facebook account?
Yes, I believe so. It's on your user profile, it sends you to facebook and you have to give LT permission.
Thank you. I connected my LT and FB accounts, but now I have problems with logging in :-(
Try to log in using your regular username and password, not via FB account.
To login via FB or Google accounts into your existing LT account, tie up them in the HybridAuth tab in your account.
The Google account services don't work with the language interfaces, different from the English one (I don't know if it's a bug). When I tried to connect my Google account with my profile, it gave me the following message :
400. That’s an error.
Application: Lyrics Translate
You can email the developer of this application at: email@example.com
The redirect URI in the request: http://lyricstranslate.com/bg/hybridauth/endpoint?hauth.done=Google did not match a registered redirect URI.
That’s all we know.
Thanks for reporting. Try it once again, now it should work.