Errors on QlikView + IIS + Web Form

[BuTbka]

Our setup: QlikView + IIS + Web Form

After upgrading to the QlikView September 2025 SR1, we encountered authorization errors.
I tried disabling the web form, and all works perfectly, but we need web form auth.

Spoiler

On the user side: Internal server error

On the server side:
Source: ASP.NET 4.0.30319.0
Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 24.02.2026 19:55:52
Event time (UTC): 24.02.2026 18:55:52
Event ID: f693f80d8c974afe9b88b08b042a43e0
Event sequence: 339722
Event occurrence: 183
Event detail code: 0

Application information:
Application domain: /LM/W3SVC/1/ROOT/QvAjaxZfc-1-134163690656279850
Trust level: Full
Application Virtual Path: /QvAjaxZfc
Application Path: C:\Program Files\QlikView\Server\QlikViewClients\QlikViewAjax\
Machine name: QLIK1

Process information:
Process ID: 8928
Process name: w3wp.exe
Account name: DOMAIN\qlik

Exception information:
Exception type: Exception
Exception message:
in QlikView.AccessPoint.User.WebFormAuthentication(Context context, String prefix)
in System.Web.UI.Control.OnLoad(EventArgs e)
in System.Web.UI.Control.LoadRecursive()
in System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Request information:
Request URL: http://qlik.domain.local/QvAjaxZfc/Authenticate.aspx?keep=
Request path: /QvAjaxZfc/Authenticate.aspx
User host address: 192.168.134.37
User: DOMAIN\user1
Is authenticated: True
Authentication Type: Negotiate
Thread account name: DOMAIN\qlik

Thread information:
Thread ID: 281
Thread account name: DOMAIN\qlik
Is impersonating: False
Stack trace: в QlikView.AccessPoint.User.WebFormAuthentication(Context context, String prefix)
in System.Web.UI.Control.OnLoad(EventArgs e)
in System.Web.UI.Control.LoadRecursive()
in System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

[ReggieHunter-4451]

Sounds familiar — after upgrades, QlikView + IIS setups often throw unexpected authorization errors. If disabling the web form fixes it, the issue is probably related to how the new SR1 handles web form authentication. Checking the QlikView server logs and IIS authentication settings usually helps pinpoint the problem.

[BuTbka]

I tried to analyze the logs using LLM, but nothing helped.