This file is invalid for the use as the following: - Security Certificate

 

This error occurs when a PKCS#7 (Microsoft IIS format) certificate file was selected during certificate enrollment.  A PKCS#7 formatted certificates are chained and cannot to be authenticated by Windows OS by double clicking on the .cer file.

 Convert PKCS#7 file into a PKCS#10 file

1. Copy and paste the certificate text into a plain text editor such as Notepad. Please be sure to include the header and footer as well as the surrounding dashes   (-----BEGIN CERTIFICATE----- and -----END CERTIFICATE-----). Do not use Microsoft Word or other word processing programs that may add characters. Confirm that there are no extra lines or spaces in the file.  Save the file as certificate.p7b.
2. Double-click the newly created file, and expand the folder that lists the name and location of the file. 
3. Click Certificates folder.  You will see three certificates under this folder: one is the SSL certificate, and the others are the Symantec Intermediate certificates.
4. Right-click the certificate issued to your common name.
5. Select All Tasks > Export
6. The Certificate Export Wizard opens > click Next
7. Select Base-64 encoded X.509 (.CER)
8. Click Next
9. Choose a file name and location for the export file (do not include an extension in your file name; the wizard automatically adds the CER extension for you).
10. Click Next
11. Read the summary and verify that the information is correct. Pay special attention to where you saved the file. Ensure that the information is correct.
12. Click Finish