The 504 Gateway Timeout error is an HTTP status code that means that one server did not receive a timely response from another server that it was accessing while attempting to load the web page or fill another request by the browser.
In other words, 504 errors usually indicate that a different computer, one that the website you're getting the 504 message on doesn't control but relies on, isn't communicating with it quickly enough.
Most of the time, a 504 Gateway Timeout error means that whatever other server is taking so long that it's "timing out," is probably down or not working properly. Since this error is usually a network error between servers on the internet or an issue with an actual server, the problem probably is not with your computer, device, or internet connection.
Suggestion to fix:
1) Retry the web page by clicking the refresh/reload button, pressing F5, or trying the URL from the address bar again. Even though the 504 Gateway Timeout error is reporting an error outside of your control, the error might only be temporary. Simply retrying the page is a quick and easy thing to try.
2) Restart all of your network devices. Temporary problems with your modem, router, switches, or other networking hardware could be causing the 504 Gateway Timeout issue you're seeing. Just restarting these devices could help.
3) Check the proxy server settings in your browser or application and make sure they're correct. Incorrect proxy settings can cause 504 errors.