Ubuntu Webserver Issue Resolution

I'm facing an issue with my Ubuntu webserver. There was an unidentified change made recently, possibly in the nginx configuration, which was reverted promptly.
I am unable to access any websites hosted on ubuntu or Plesk also hosted on the server.
There is no remote access to the server so this could make it difficult to diagnose.


Key Tasks:
- Diagnose the root cause of the issue causing the webserver to be inaccessible externally
- Resolve the issue and ensure the webserver is reachable from external networks

Skills and Experience:
- Proficiency in Ubuntu and webserver administration
- Strong understanding of networking and firewall configurations
- Experience with nginx or similar webserver software
- Troubleshooting skills to identify and rectify the issue
- Ability to work efficiently and communicate clearly throughout the process.