Admin AJAX doesn’t work in plugin admin page – Even though code is copied verbatim from WordPress Codex

Your AJAX add_action and associated callback function shouldn’t be inside view-create-rooms.php, move it into your main plugin file. When an AJAX request is sent, you’re making a new separate request to the server, so your submenu page will not be loaded and your AJAX action never gets added to the queue.

404 Not Found

Not Found

The requested URL was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.