I have set up our website on IIS 7.5, out of the blue single sign stopped working at all.Users are getting continuous popup for username/password. I tried every thing I could find on internet, following items have been checked: 1. Anonymous authentication is disabled. Windows authentication is enabled. 2. My identity account in app pool is having access to the files and folders of web site, it is added as an admin in the server as well. 3. I cross checked the settings in internet explorer -> internet options, they are in proper shape.
My website was working properly till yesterday, can anyone suggest what might have gone wrong? When I was setting it up for the first time, I faced the similar issue. I suspected because of my application pool it was happening, I tried/experimented with the pool, (selecting default app pool then again selecting my newly created app pool) and it worked after few tries. This is really important for me, I would appreciate if any one can suggest something. I might be missing something in app pool.
I went through the log files as suggested by @LexLi: sc-status - 401 and sc-substatus 2, I dont know if I am referring to the information in this link correctly -https://support.microsoft.com/en-ca/help/943891/the-http-status-code-in-iis-7-0-iis-7-5-and-iis-8-0 I says 401.2 - Logon failed due to server configuration, but I have not made any changes on the server.