Password prompt

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 This typically happens when the user selects the Keep me signed-in check box. For federated user accounts, the user name and passwords are not saved. This is because Integrated Windows Authentication can be used, which does not require the password. For a third-party federated identity provider that does not support Integrated Windows Authentication, the password is not available from CredMan, and therefore it must be prompted for.

Here is the fix that you can try

1. Start Registry Editor.

2. Navigate to the following registry subkey:

   Office 2016

   HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity

   Office 2013

   HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Common\Identity

3. Right-click the entry, and then select New.

4. Add a new DWORD value to the registry called NoDomainUser, and then set it to a value of 1.

The registry entry alters the behavior for a federated user account so that the password is saved in CredMan.