Fix 504 Gateway Error

I need help resolving a 504 Gateway time-out error on my WordPress site. The error appears on the entire website, and I haven't made any recent changes to the server or hosting settings. I made a fresh install of a new Wordpress installation and it is affecting this too.

Key Details:
- WordPress site
- Error on entire website
- Caching plugins are active

Ideal Skills and Experience:
- Expertise in WordPress troubleshooting
- Experience with server errors, particularly 502 Bad Gateway
- Familiarity with caching plugins and their configurations
- Knowledge of server and hosting settings related to WordPress

Please provide a brief overview of your approach and relevant experience.