(below details are copy-pasted from Microsoft forum)
Some of our users' Outlook stop syncing with Exchange and ask for a password.
But when we press the "Need Password" button, nothing happens. There is no prompt.
To fix the issue, I cleared entries in Credential Manager, deleted temporary files, unchecked "Use Cached Exchange mode", restarted the system, and checked again.
POST 2: (Confirmed accepted answer)
There are a number of reasons for this. First, I would look inside the Office 365 admin portal to make sure your password expiration policy is not set to only a few days.
If this is okay, setting the below registry key to 1 in the following path often resolves it:
Path: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity
Key: DisableADALatopWAMOverride (DWORD)
This key may not exist; we need to create it.
This also works https://docs.microsoft.com/en-us/outlook/troubleshoot/authentication/outlook-prompt-password-modern-authentication-enabled