Unable to connect using windows login

I am trying to connect to users within my company to assist them, but need to connect with windows login to connect as admin so I can install applications. It used to work but now I am getting an error that the password is invalid, even though I am certain that the password I am entering is correct. Have tried with multiple users, and a test machine, getting same results. Have set Extras/options/security/Windows Logon/Allowed for Administrators only on the user's machine, or using QuickSupport, same results either way.