When logging into FYI, I keep being asked to login with my authenticator.
I have set "Stay signed in for 30 days" but I am still being asked to login.
Multi-Factor Authentication is turned on in your Microsoft 365 account.
When Multi-factor Authentication is turned on, users in your organization need to enter the authentication code to verify identity when they login to Office 365 on the browser. This is actually a default behaviour.
If you feel this is an inconvenience, a Microsoft365 admin user has the option to bypass Multi-Factor Authentication verification. For more details, you can refer to Remember Multi-Factor Authentication part in the Microsoft help article Configure Azure AD Multi-Factor Authentication settings.