When clicking on the SHA2 signature algorithm SSL certificate issued by WoSign on Windows 2003 Server, a certificate error message is displayed. This may be because the certificate file is damaged when FTP transfers the certificate public key file.
Please click "Details" again. If you see "Signature Algorithm: 1.2.840.113549.1.1.11" as shown in Figure 2 below, then it excludes the possibility that the file has been damaged. It must be Your Windows 2003 Servre does not support the SHA256 signature algorithm.
You need to download the Microsoft HotFix KB968730 patch (X86 platform Chinese, X86 platform English, X64 platform Chinese, X64 platform English). After installation, the SHA256 signature algorithm will be displayed normally