Unknown login, trying to change password but can't

I just got an email that there was a login to my server, with my username, in Italy. I live in the US.

I login using my linked Google account. When I try to change my password on plex.tv/users/edit it won’t let me. I enter a new complex password that meets the criteria and my current password but then it says “Invalid Password”.

What am I doing wrong? Has this hacker already changed my password somehow?

Please contact https://www.plex.tv/contact/?option=plex-pass-billing

Thanks! Just did that. Anything I can do in the meantime to safeguard my account?