SharePoint Admin User Login Loop

Question

I am currently working on a project where i have to make a sharepoint server(hosting it through Azure). The problem i am having is when i am accessing my SharePoint site on my server as an admin user, it will prompt for authentication and when I put in the credentials in the login prompt it loops and keeps asking for the credentials instead of passing it through. The error it shows in the browser console is 401 Unauthorized. Any ideas of what's causing and how to fix it?

Answer 1

Hi @Theisen Reddy 
Thank you for posting your question in the Microsoft Q&A forum. 

Based on my research, this issue is typically caused by authentication protocol mismatches when using Integrated Windows Authentication like NTLM or Kerberos over HTTP/2 or HTTP/3. These protocols are not compatible with IWA, and IIS (commonly used by SharePoint Server) defaults to HTTP/2, which can trigger the login loop. 

You can read more at HTTP/2 on IIS | Microsoft Learn 

To resolve this, you may need to: 

-Disable HTTP/2 and QUIC on the IIS site hosting SharePoint Server. 

-Enable Negotiate and NTLM Providers in IIS. 

For more information about IIS, please access Getting Started with the IIS Manager in IIS | Microsoft Learn 

-Clear cookies and cache or try a different browser. 

I also found this helpful thread, while this is for SharePoint Online, the concept may apply if you are using hybrid configuration. You may take it as a reference Unauthorzied 401 while accessing sharepoint - Microsoft Q&A 

I hope this helps. 

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