I am pretty sure there is no way that someone else is logged in to my acc. There should be way to check active sessions, logout other sessions or next login should kill all previous sessions.
Hello Tadeusz,
the testing phase ended on the 20th of March, you will be able to log in on our next test (of course you need to be with a Supporter or Honored account status) which will happen in about 4 to 6 months.
You are receiving a message that you are "Already logged in" because your version is out of date and the updates are postponed at the moment.