It seems that Cloudflare is protecting too much Elementor API rest.
To test it, edit a new page into your site, named test.php and add
<?php
$xml = file_get_contents("https://my.elementor.com/api/connect/v1/library/templates");
echo $xml ;
?>
Go to your domain/test.php and see if you get a 403 Forbidden error. In this case , God help you, I got my share of swearing with my Hosting and Elementor, being in the middle of it.
If that is the case, I stil did not find who is to blame, if any progress I will tell you for sure !
