Hi,
A 503 error usually has something to do with an overloaded server or server maintenance. Of course, since you only get this when trying to open Elementor, it’s probably not the case that the server is undergoing maintenance since other pages would be affected as well.
The most probable culprits are heavy PHP scripts. These might be loaded alongside Elementor as you’re trying to update the editor. You can try disabling plugins that are loaded alongside the Elementor editor and see if that helps. This could also go away on its own if you’re using shared hosting and the servers are being overloaded at the moment. You could also try switching your Theme, as these can also be causing a heavy load with their PHP scripts.
If you’ve disabled all plugins except for Elementor, and you’re still getting this error, you could try reinstalling the Elementor plugin.
You can also refer to this article to see if some of these solutions help:
https://www.wpbeginner.com/wp-tutorials/how-to-fix-503-service-unavailable-error-in-wordpress
Ultimately, this is definitely related to the server, so contacting your hosting provider might provide you with a direct solution for the issue, or they might point you toward what the problem is.
?