I installed 3 plugins (debug bar and its addon). It’s the debug bar menu in the admin toolbar.
In the remote requests, you’ll see all outgoing requests and it doesn’t display the request to our server. Which means something is blocking it. So I tried the console to issue a remote request to our server and got 404, but I can’t get the details of the result.
My initial finding is, the request to our server is being overridden by something else, or being blocked. Would you mind providing your FTP login credentials as well? Maybe I’ll directly test the result from theme’s request.