Sysadmin for Redirect and Configuration Issue Resolution

PLEASE NOTE: you MUST have PLESK experience since PLESK is compiling and doing things. I had a developer yesteday who could resolve the issue, but it was outside of plesk and the site runs under plesk.

Description:
I am looking for an experienced System Administrator to diagnose and resolve a persistent redirect loop on a Magento 2.4 site running on Plesk 18 with Ubuntu 22.04.

The issue started after an SSL certificate update with Let's Encrypt and has persisted despite extensive debugging. The development environment, which does not use Varnish and Redis, works fine, but the live instance, which includes Varnish and Redis, is stuck in a redirect loop.

Issue Overview:

1. SSL Certificate Update
- SSL was renewed via Let's Encrypt.
- _acme_challenge tokens were added for validation under robot.hetzner.com.
- After SSL renewal, the site went into a redirect loop.
- Removing the _acme_challenge tokens did not fix the issue.
- Other domains on the same server using Let's Encrypt work fine.

2. Varnish and Redis Configuration
- Varnish initially conflicted with Plesk's admin interface on port 8443.
- Fixed by changing Varnish ports to 6081 and 6082.
- Redis is running without issues.
- Varnish’s role in redirects may still be affecting site behavior.

3. Magento Redirects and htaccess
- Cleared Magento’s URL redirect table, but the issue persisted.
- htaccess files are identical in dev and live environments.
- No recent changes to htaccess or Magento configurations.

4. Server Details
- Hosted on Hetzner with a dedicated server.
- Runs Plesk 18 with Ubuntu 22.04.
- Nginx is a reverse proxy for Apache.
- Other domains on the server work fine.

Latest Findings:
- NGINX Permissions Play a Key Role
- When the site is set to nginx:nginx privileges, the site works.
- When reverting to its previous state, the redirect loop returns.
- Switching back a third time completely breaks the site.
- Tested if Nginx is running and handling requests instead of Apache.

Suspected Causes:
- SSL Misconfiguration – Let's Encrypt settings, certificate chain, or how Plesk handles SSL renewals.
- NGINX Handling Issues – Potential misconfiguration causing conflicts between Apache and Nginx.
- Plesk Auto-Generated Configurations – Plesk may be altering SSL, virtual hosts, or permissions when updating the certificate.
- Varnish or Redis Conflict – Even after fixing Varnish ports, it might still interfere with redirects.
- Server-Level Issues – Possibly introduced during an automatic update affecting Nginx, Apache, or Plesk.

Task Requirements:
- Investigate and resolve the Magento 2.4 redirect issue.
- Check and validate Varnish, Redis, Nginx, and Apache configurations.
- Verify SSL setup and troubleshoot Let's Encrypt certificate handling.
- Ensure Magento’s redirect logic functions correctly.
- Fix any Plesk misconfigurations affecting redirects.

Skills and Experience Required:
- Advanced System Administration with Linux, Ubuntu 22.04, and Plesk 18.
- Magento 2.4 Server Configuration with experience in live and dev environments.
- Deep expertise in Varnish, Redis, Nginx, Apache, and debugging caching conflicts.
- Strong knowledge of SSL Certificates and Let's Encrypt including ACME challenges, auto-renewal, and debugging.
- Ability to debug and resolve permission-based redirect issues.

Additional Notes:
- This is not a beginner-level job. You must have proven experience in Magento 2.4, Plesk, Varnish, and SSL troubleshooting.
- Urgent issue. The site is currently down, and immediate resolution is required.
- Do not apply if you do not have expertise in debugging these specific configurations.

How to Apply:
- Briefly explain your experience with Magento 2.4, Plesk, Nginx, Apache, and Let's Encrypt troubleshooting.
- Provide examples of similar issues you have resolved successfully.
- Be ready to start immediately. This is a high-priority task.