Forms authentication provider stops working after applying May CU for SharePoint 2013
After we installed May CU for SharePoint 2013 (15.0.4823.1003) we were not able to log with Forms authentication users and the error (404) In SharePoint log we could see the error: Exception trying get context compatibility level: System.IO.FileNotFoundException: The site https://dax2012r3.contoso.com:8090/_Layouts/FormsAuth/Login.aspx could not be found in the Web application SPWebApplication Name=DynamicsFormsSTS – dax2012r3.contoso.com-8090. at Microsoft.SharePoint.SPSite.LookupSiteInfo(SPFarm