entity framework 6 - Why do i get a 404 on some users from the same application on ASP.NET Core on IIS -

i new asp.net, iis , webapplications, maybe question quite stupid, have searched 3 days , don't :-(

i have build application in asp.net core 1.1 using ef6 on full framework 4.5.2. build scratch using windows authentification. once had little bit show published site on server iis 8.5 running. site works, in our company authenticated , still is.

meanwhile working on site , added new features, including novell.directory.ldap.netstandard package. because of package changed target framework 4.6.

now fun part... published upgraded site on iis using exact same configuration. site works expected. 50% of users ends in 404 error , blank screen. if same users starts "old" site can use expected.

has idea, problem be, or @ least how can find out going wrong exactly?

btw not able debugging on server, since protected smartcard.

maybe there trick debug error page on iis express?

thanks in advance thoughts :-)

edit: ok, found out. problem comes windows authentification. on machines (users?) user.identity.name returns null

edit 2: web.config

<configuration>   <system.webserver>     <modules runallmanagedmodulesforallrequests="true" />     <handlers>       <add name="aspnetcore" path="*" verb="*" modules="aspnetcoremodule" resourcetype="unspecified" />     </handlers>     <aspnetcore forwardwindowsauthtoken="true" processpath=".\docudatwebapp.exe" stdoutlogenabled="false" stdoutlogfile=".\logs\stdout" />     <httpprotocol>       <customheaders>         <add name="x-ua-compatible" value="ie=11" />       </customheaders>     </httpprotocol>     <security>       <authorization>         <remove users="*" roles="" verbs="" />         <add accesstype="deny" users="?" />         <add accesstype="allow" users="*" />       </authorization>     </security>   </system.webserver> </configuration> 

and here program.cs

    public class program     {         public static void main(string[] args)         {             var host = new webhostbuilder()                 .usekestrel()                 .usecontentroot(directory.getcurrentdirectory())                 .useiisintegration()                 .usestartup<startup>()                 .useapplicationinsights()                 .build();              host.run();         }     } } 

edit 3 ok, gave on windows authentication , switched oidc. working fine.