This issue comes sometimes because of server license issue, authentication issue or sometimes web server issue. kindly make it sure,
1. your server license is correct
2. IIS service is running and have rights to the document folder if not than try giving iis_isurs read access to your documents folder ()C:\Programdata\Qliktech\Documents) is worked for me
3. also please look at the folder you have mounted in qlikview server, is it the same where your documents are lying
4. if all fine than open qlikview management console -> system tab -> setup tab -> qlikview web servers -> authentication tab : in authentication tab make the authentication to point at always and than go to access point and check your documents, they should be working by now.
if issue is not solved than also please look at these settings of Qlikview Server and Web Server.
Authentication Client : Allow anonymous
Authorization : DMS authorization(QlikView controls file access)
QlikView Web Server:
Authentication : Always
Type : Custom User
Parameters Prefix : CUSTOM\
Login Address : Default login page
Let me know if problem is not resolved.