I am using userProfileLookup function on my Nintex Form (188.8.131.52) (SP2013 on prem).
when a user is entered in the people picker , i am using calculated value control to get the user profile info.
Sometimes it is asking for username and password. But the WorkEmail, department , preferredName display correctly all the time. FirstName, LastName ,workphone and some other custom fields does not display.
Most of the time all of the fields display without any problem.