It seems that SSO (Single Sign-On) is not enabled for this user. You can do this:
Make sure that the QlikView user is authenticated with a Windows account in the current QlikView server domain or at least in a domain with a trust-relation with the QlikView server domain
In IE11 on the users PC/Laptop, select Internet options->Security->Local Intranet Zone and click the Custom Level... button. In the options tree, scroll down to the bottom and in User Authentication->Logon, select Automatic logon with current user name and password.