An SSL Certificate cannot be issued: Could not issue a Let's Encrypt SSL/TLS certificate for example.com

Symptoms

1. Attempting to issue an SSL Certificate via Domains > example.com > SSL/TLS Certificates > install Let's Encrypt Certificate results in the following error:

PLESK_ERROR: Could not issue an SSL/TLS certificate for example.com
Details
Could not issue a Let's Encrypt SSL/TLS certificate for example.com.

2. The following errors can be found in %plesk_dir%admin\logs\php_error.log:

CONFIG_TEXT: [2025-04-24 14:41:42] 11668:680a07530e8bc DEBUG [extension/letsencrypt] pm_Exception: Unable to execute command extension: proc_open(): Command conversion failed
file: C:\Program Files (x86)\Plesk\admin\plib\pm\ApiCli.php
line: 269 code: 
0 trace: 
#0 C:\Program Files (x86)\Plesk\admin\plib\pm\ApiCli.php(60): pm_ApiCli::execSimple(string 'extension', string '"C:\Program Files (x86)\Plesk\bin\extension.exe"  --call sslit --common-challenge-dir -info -format ...', integer '1', array, string '')
#1 C:\Program Files (x86)\Plesk\admin\plib\modules\letsencrypt\library\PleskCli\PleskCliService.php(23): pm_ApiCli::call(string 'extension', array, integer '1')
#2 C:\Program Files (x86)\Plesk\admin\plib\modules\letsencrypt\library\Environment\CommonChallengeDir.php(73): PleskExt\Letsencrypt\PleskCli\PleskCliService->call(string 'extension', array)

3. The folder C:\Windows\System32 is missing from the Path System environment variable.

Cause

The C:\Program Files (x86)\Plesk\admin\plib\pm\ApiCli.php utility cannot open a process since Path System Environment Variable is missing C:\Windows\System32, which results in failure to issue an SSL Certificate.

Resolution

To add the System Environment Variable, do the following:

1. Press Win + R, type sysdm.cpl, and press Enter.
2. Go to the Advanced tab.
3. Click Environment Variables.
4. Under System variables, find and select Path, then click Edit.
5. Click New and add: C:\Windows\System32
6. Reboot the server to apply the changes.