The error message "client denied by server configuration" typically indicates that the Apache web server is denying access to the requested resource based on its configuration.

Here are steps you can take to troubleshoot and resolve this issue in Plesk:

1. Check Apache Error Logs:

   • Start by checking the Apache error logs. These logs can provide more specific information about why access is being denied. The error log files are usually located in /var/log/httpd/ or /var/log/apache2/.

2. Verify Directory and File Permissions:

   • Ensure that the file and directory permissions are correctly set for the affected website's files. The directory containing the files should have appropriate permissions for Apache to read and execute files.

3. Check .htaccess Files:

   • Review any .htaccess files in the website's directories. They may contain directives that deny access. Make sure there are no restrictive rules that might be causing the 403 error.

4. Review Apache Configuration:

   • Check the Apache configuration files for the specific virtual host associated with the affected website. Verify that there are no directives that deny access to the location or file in question.

5. Verify IP Deny Rules:

   • Ensure that there are no IP deny rules in place that might be blocking the client's IP address. These rules can be set in Apache configuration files.

6. Check for Directory Index Settings:

   • Ensure that the directory containing the website files has a valid index file (e.g., index.html, index.php) defined. If not, Apache might be trying to list the directory contents, which could be restricted.

7. Check for Custom Security Modules:

   • If you have custom security modules or rulesets installed, review them to ensure they are not causing access denial.

8. Verify IP-Based Restrictions in Plesk:

   • In Plesk, go to the domain settings and check if there are any IP-based restrictions set. These restrictions might be blocking the client's IP address.

9. Restart Apache:

   • After making any configuration changes, restart Apache to apply the new settings:

     bashCopy code

     sudo systemctl restart apache2 # On Debian/Ubuntu sudo systemctl restart httpd # On CentOS/Red Hat

10. Check for Firewalls or Security Software:

    • Make sure that there are no external firewalls or security software (like ModSecurity) that might be blocking access.

11. Review Recent Changes:

    • Consider any recent changes or updates that might have affected the server configuration. Undoing recent changes might help resolve the issue.

If you've followed these steps and are still experiencing the issue, it's recommended to consult the specific error messages in the Apache logs for further details. Additionally, you may want to consider reaching out to Plesk support for more specialized assistance based on your server's configuration.