VERIFIED SOLUTION i

Resolving - Windows authentication fails in HQ for Portrait Dialogue users

Issue

Portrait Dialogue, HQ users are prompted for username and password when accessing HQ but fails to login

Cause

The Dialogue user and/or IIS is not properly configured

Resolution

UPDATED: October 6, 2017
Confirm the User in the IIS Application Pool and Dialogue. 

In IIS browse to Application Pool then locate the Portrait Shared Server AppPool.
Right click and select "Advanced Settings".
In the Advanced Settings window, the Identity is located under the Process Model section.  
It is recommended that a special domain user (i.e pcmsysuser) is created for this purpose. 
Note the user.

Next go to Dialogue and review the Access Rights in the User Properties for this same user in Dialogue Admin.
This user has to be a member of the System Administrators group, have the user permission "Allow user to create user sessions for other users" set.