For some reasons, you may have to run IIS Express x64 from VS2012. For later versions, it is automatically instantiated, however in case of VS2012, it isn’t. And there is no way Microsoft provides any patch or upgrade.
Although there is untestable hack or trick which did work for me.
You have to modify registry to invoke or run IIS Express x64.
Create batch file (*.bat) and put below code.
reg add HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0\WebProjects /v Use64BitIISExpress /t REG_DWORD /d 1