Hi Andy Lo,
You can try the steps in the following link:
Troubleshooting verification code issues - Microsoft Support
Since your issue is more related to account, please kindly understand that the Outlook tag here we mainly focus on general issues about Outlook desktop client. In order to better solve your problem, it's suggested that you could post your case in dedicated forum for Outlook.com for more professional advice.
Thanks for your support and understanding!
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.