微信确认有BUG：
https://support.microsoft.com/en-au/help/3007507/-http-error-500.19-error-when-you-browse-an-iis-8.5-website-in-windows
尝试以下HOTFIX:
Windows Server 2012 RTM http://hotfixv4.microsoft.com/Windows%208/Windows%20Server%202012%20RTM/nosp/Fix5342456/9200/free/489291_intl_x64_zip.exe)
Windows Server 2012 R2 http://hotfixv4.microsoft.com/Windows%208.1/Windows%20Server%202012%20R2/sp1/Fix524097/9600/free/479017_intl_x64_zip.exe