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

Symptoms

• When uploading an SSL certificate to Plesk, the operation fails with:

  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.

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. Make sure that Private Key starts with:

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

3. Start a command prompt as an Administrator.

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

   C:\> "%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.