There are many HTTP status codes sends to the users and one of them is 504 gateway timeout error and this error occurs when your request is unable to complete by servers. When you visit any site then the site grants your request and sends it to web servers and if your request is unable to complete then the server sends back the error to you.

To know that what is 504 gateway timeout and what does 504 gateway timeout mean then you need to read this content.

504 gateway timeout error is a server-side error and this error occurs when the servers are not able to complete a request due to miscommunication between the servers.

https://www.cuesinfo.com/blog/504-gateway-timeout-error/