Hey there! Nice to meet you!
I'm sorry you are experiencing this.
If I may ask, have you forgotten your account's password by any chance?
If not, may I know the exact error message upon signing in?
Do you still have access to all of your account's security information, email, or phone number?
Do you see any unfamiliar email addresses/phone numbers upon signing in to your account?
Did you have two-factor authentication (2FA) active on the account? If yes, do you have the 25-character recovery codes?
Lastly, may I know when was the last time you successfully signed in to your Microsoft account?
Best regards,
Darhyl