Sending, receiving, and organizing email in Outlook.com
Visit your Microsoft account: https://account.microsoft.com and look for any of these:
- Verify your identity
- Unusual activity detected
- Action required
- Account temporarily limited
Sometimes new accounts require an additional verification before they're fully functional.
If above check will still fail and considering the account is only about 20 hours old, I'd suggest to wait until the account has been active for 24–48 hours, as mailbox provisioning can occasionally take longer than expected.