Hello, thank you for reaching out to Microsoft Q&A.
I understand you're having trouble signing in to Office 365 and Outlook with your Microsoft account.
If you receive a "Too many requests" error, try this method.
- Use an Incognito tab on any web browser and sign in with your Microsoft account - https://account.microsoft.com/
- Enter your Username (Email address) first.
- Next, don't type your password. Instead, select 'Use another way to Sign in', and sign in with your Microsoft account using the alternate security email address or Phone number.
- Enter the Verification code and sign in.
If you're able to sign in, go to the " Manage How you Sign in with your Microsoft account page, and enable two-factor authentication. If 2FA is already enabled, add the Microsoft Authenticator app. So, you can use your authenticator app to sign in on Office 365 and Outlook apps.
Let me know if you still need more help.