Hi,
This is a server-related error: "The ERR_CONNECTION_TIMED_OUT error in a web browser indicates that the browser failed to establish a connection with the website's server within the allotted time". You can see more on google: "https://www.google.com/search?q=err_connection_timed_out".
WordPress or Themes, Plugins are just some of the resources on your server. The way a web browser works is: when you access a domain, the web browser will send a request to the server corresponding to that domain, then the server will return the resources (including WordPress, Themes, Plugins), at this time the browser reads those resources and displays them to the viewer.
The error in the image you sent is an error from the very first step (when the web browser sends a request to the server but receives nothing back). Please check your server or hosting again.
Regards!