Add the handler mapping to IIS
<handlers>
<add name="*.seo-4.0_32Bit" path="*.seo" verb="*" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" resourceType="Unspecified" preCondition="classicMode,runtimeVersionv4.0,bitness32" />
</handlers>
If extension not worked, add following between <system.webServer>
<modules runAllManagedModulesForAllRequests="true" >
<remove name="UrlRoutingModule"/>
</modules>
<handlers>
<add name="*.seo-4.0_32Bit" path="*.seo" verb="*" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" resourceType="Unspecified" preCondition="classicMode,runtimeVersionv4.0,bitness32" />
</handlers>
If extension not worked, add following between <system.webServer>
<modules runAllManagedModulesForAllRequests="true" >
<remove name="UrlRoutingModule"/>
</modules>