Gmail account blocked?

I have had a Gmail account for about a year. I only log in with my own laptop, which is always on my desk.

Yesterday I could not log in with my login because I wanted to log in "with an unknown device". I was able to open the account again with a second email address. But how can that be? Has someone here tried to open my account?

Probably a kind of security check. For me the "account expired" at some point because I never used it…

I only log in with my own laptop

And there was probably a cookie on it - and that probably expired yesterday.