I did not mean that someone has access to your account, but to your PC. For example, if you have a sibling or a friend with their own account and a beta access, and if they used your PC. Sorry if there was any confusion.
If that’s not the case, but you’re seeing an option for the Beta, I’m afraid that only accounts with a license to the Beta will be able to access the game. You can find more information here, if needed: