If you have Microsoft Multi-Factor Authentication enabled, Outlook and other applications may not accept your password. This is due to the application not 'understanding' modern authentication.  If you are prompted for a password, then try following this guide to update the Office application first >> Update Office 365 Applications

If Outlook is not connecting and showing a password prompt, use the instructions below to create a single use application

Creating an Application Password

1:Once logged in to your office portal (Sign in HERE) at the top right, click on your little Circle (1) and then Edit Account (2)

2: When this page loads, click on (3) Security Info

3: Click on Add method (4)

4: When this window pops up click on the Drop Down (5) and the select App password, then click on Add (6)

6:Type in a description in (7) for the password, like Outook Password and then click on Next (8) 

7:Microsoft will then generate you a password, copy that password (9) and once you have it click on Done (10)

8:You will now see that App password listed, the only option you have is to delete that password.

Note: That you will only every see the password once, when you have created it, it can not be revealed again!

Using the password

You can now enter that password into any Microsoft Application that is not accepting your password and MFA code.For example Microsoft Outlook
  1. Check that is your  (1)
  2. Paste in your password (2)
  3. Check the Remember my credentials (3)
  4. Click on OK

If you have saved you App password within a file, then you should delete that file, you can always create another APP password if required.