Do you have other accounts besides Netflix where you use the same email address and password? If so, they might have discovered your information through a website leak. Use a separate password on each site, and change the passwords on all the ones that are currently using it.
If the password is straightforward, they might have only made a fortunate guess.Check your computer(s) for any malware or other nasties that might be leaking your private information.As Nick T. pointed out, it might simply be a case of someone trying to log in but using the erroneous account name.To log out of all your devices, which will also log out any rogue devices, visit the Netflix website after changing your password. Then sign in to your devices once more using the new password.
This may be the result of the fact that different individuals and places have access to your password.Netflix may sign you out of all other devices if it detects usage of its software because it may be concerned that your password has been hacked.You could also lose access to your account if you shared your password with numerous individuals across different places.You can block someone from using your Netflix account if you believe they are doing so by doing the following actions:Open a web browser and log in to your Netflix account.Select "Account" from the dropdown menu by clicking on your profile icon in the top right corner.Go to "Settings" and select "Sign out of all devices."Verify your desire to log out of all devices.This will sign out anyone who was logging into your Netflix account without your permission as well as all devices that are currently utilizing it.It's crucial to make sure your password is secure and difficult to guess if you don't want to change it. For even more security, you can enable two-factor authentication. Furthermore, you should consistently check your account for any fraudulent activity and, if found, report it to Netflix. Contact Netflix Help Centre to fix Netflix Password issue.