IIS 10 - Windows Authentication - AuthenticationType "unavailable" -

i web app i'm trying working windows auth. however, no matter do, can't past 401.

web.config

<configuration>   <system.webserver>     <security>       <authentication>         <anonymousauthentication enabled="false" />         <basicauthentication enabled="false" />         <windowsauthentication enabled="true">           <providers>             <clear />             <add value="ntlm" />           </providers>         </windowsauthentication>       </authentication>       <authorization>         <clear />         <add accesstype="deny" users="?" />         <add accesstype="allow" users="cable\mmulhe200" />       </authorization>     </security>     <tracing>       <tracefailedrequests>         <add path="*">           <traceareas>             <add provider="www server" areas="authentication,security,staticfile,cgi,compression,cache,requestnotifications,module,fastcgi,websocket" verbosity="verbose" />           </traceareas>           <failuredefinitions timetaken="00:00:00" statuscodes="401.1" />         </add>       </tracefailedrequests>     </tracing>   </system.webserver> </configuration> 

iis failed request trace output (partial)

<failedrequest url="http://dev.windowsauthtest.com:80/"                siteid="3"                apppoolid="windowsauthtest"                processid="33204"                verb="get"                authenticationtype="not_available"               activityid="{80000727-0003-f400-b63f-84710c7967bb}"                failurereason="status_code"                statuscode="401.1"                triggerstatuscode="401.1"                timetaken="0"                xmlns:freb="http://schemas.microsoft.com/win/2006/06/iis/freb"                > 

the part concerns me is

authenticationtype="not_available" 

i prompted enter credentials , enter nt username/password , keeps re-prompting.

any ideas?