Hi!
Are you able to access your email on another device?
- Try accessing https://outlook.live.com/mail/ in a computer browser or another mobile phone.
Have you tried another verification method, such as a code via the recovery email, or an Authenticator? Or is it not configured?
If it works on another device
Reinstall Outlook on your iPhone. You must remove the account in iPhone settings > accounts (if present) before reinstalling the app.
If it doesn't work on another device
Check if your account is locked using Sign-In Helper.