Hi @Pat Clifford
Thank you for posting your question in the Microsoft Q&A forum.
I'm sorry to hear you're having trouble logging into your email. As I understand, you cannot log into your Outlook (Microsoft) account due to the Error 400. Please try the following troubleshooting steps, which have been effective in similar cases
Please try logging into your Microsoft account again using a completely different network (Wifi, Mobile Data), device (laptop, computer, mobile phone) and method (Outlook on Web, Desktop App or Mobile App).
Clear your browser cache and cookies
Use a VPN to connect from a different region or IP Adress
The other thing you can do is try this in New InPrivate window
Please add a new account in Outlook.com or New Outlook and check if you can log in and access the email account Add an email account to Outlook for Windows - Microsoft Support
In case you use a personal account, you can recover your account using the Microsoft account recovery form, when you fill out the account recovery form, make sure to provide as much information as possible and correctly https://account.live.com/acsr
Please give those troubleshooting steps a try. As a moderator, I do not have direct access to Microsoft's internal systems needed to troubleshoot this effectively due to privacy and security constraints. If the problem remains, I kindly suggest that you escalate this matter to the Contact - Microsoft Support
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 .