Hi, Beom,
My name is Didi. I'm happy to help you today.
You may need to contact the org's IT admin to configure the settings below.
- Sign in to https://portal.azure.com > Azure Active Directory
- Go to Enterprise Applications > Microsoft Teams > Properties
- Enable for users to sign-in? : YES
https://answers.microsoft.com/en-us/msteams/for...
Best regards,