Along with Microsoft's announcement of the SHA-1 deprecation policy, they also provided information that the Windows 2003 Server can no longer use the SHA-1 certificate in SSL connection, but SHA-2 instead.
When Windows 2003 tries to establish an SSL connection to SPS URLs with a SHA-2 certificate, the following error may occur and cause connection failure, which can be observed in the ofcdebug.log:
2016 09/26 10:43:57 [0d5c : 0d60] (00) (W) [cgiShowClientAdm][cgiShowClientAdm.exe][CWinHttp::WinHttpRequest] Error code 12175 - [libWinHttpWrapper.cpp(253)]
This article discusses how to solve this error.
This error occurs because the Windows 2003 server did not install the required hot fix. Please install the Microsoft Hot Fix in KB 968730 to solve this issue.