Unable to set the private key in Plesk for Windows: Probably, the private key format is invalid

Symptoms

• Certificate uploading to Plesk fails with error:

  PLESK_ERROR: Unable to set the private key: Probably, the private key format is invalid

• Private Key in the .key file starts with:

  CONFIG_TEXT: -----BEGIN PRIVATE KEY-----

• The following error message appears in the Plesk logfile %plesk_dir%admin\logs\php_error.log:

  CONFIG_TEXT: ERR [panel] Unable to set the certificate: Incompatible private key/certificate pair..

• In some cases, domain reconfiguration fails with the following error message:

  PLESK_INFO: stdout:
  A specified logon session does not exist. It may already have been terminated. (Exception from HRESULT: 0x80070520)
  In Microsoft.Web.Administration module
  Exception type: System.Runtime.InteropServices.COMException
  at Microsoft.Web.Administration.Interop.IAppHostMethodInstance.Execute()
  at Microsoft.Web.Administration.BindingManager.Save()
  at Microsoft.Web.Administration.ServerManager.CommitChanges()
  at ServerManagerFactory.commit()
  at IISServerManager.commit(IISServerManager* )

Cause

Certificate Private Key part is encrypted.

Resolution

1. Connect to the Plesk server via RDP.

2. Save the Private Key part in a text file, for example C:\Temp\my_encrypted.key.

   Note: Make sure that Private Key starts with -----BEGIN RSA PRIVATE KEY-----:

3. Start a command prompt as an Administrator.

4. Decrypt the key using the openssl utility with these commands:

   C:\> cd C:\Temp
   "%plesk_bin%\openssl.exe" rsa -in my_encrypted.key -out my_decrypted.key

   where:

   • my_encrypted.key - is an uploaded file from step 2
   • my_decrypted.key - a decrypted file that will be created

5. Use the new decrypted .key file (In this example, my_decrypted.key) to upload an SSL certificate in Plesk.