Hey Andrew! Nice to meet you!
Based on your description, the 401 error code was due to a server issue, but since there are no server alerts for Outlook: https://portal.office.com/servicestatus/ kindly try to perform the following workarounds for us to isolate the case:
(You may skip the parts if you have done them already.)
- Restart your device and router, then try signing in again.
- Clearing the cache and cookies of your browser.
To clear your browser cache and cookies in Microsoft Edge, go to Settings > Privacy > Clear browsing data and select Ctrl+Shift+Del. You can also type "edge://settings/clearbrowserdata" in your address bar to access this function.
- Disabling extensions / going incognito or in-private browsing.
In Microsoft Edge, select Extensions located to the right of your browser address bar, then select Manage Extensions.
Select the toggle next to the extension you want to turn off.
- Changing browsers. (Google Chrome, Microsoft Edge, Safari, etc.)
- Disconnect from the VPN or Proxy server.
Open Settings and click/tap on the Network & Internet icon.
Click/tap on VPN on the left side, click/tap on the connected VPN (ex: "MPN") on the right side you want to disconnect, and click/tap on the Disconnect button.
When finished, you can close Settings.
- Using different devices and network services.
7.Try waiting a few hours to sign in again.
You may also try the Sign-in helper tool in case this would work through this link: https://support.microsoft.com/account-billing/i-can-t-sign-in-to-my-microsoft-account-475c9b5c-8c25-49f1-9c2d-c64b7072e735
Thank you for your kindness and understanding! Please feel free to let me know if you need anything else.
Best Regards,
Darhyl