fifthelement

@webmatpro yes, the bug is in the jet theme core module for Elementor.
It uses a method name that was deprecated and no longer supported in Elementor 7.2.1.

open the file wp-content/plugins/jet-theme-core/includes/locations.php
Replace line 114
AS IS
$css_file = new Elementor\Post_CSS_File( $template_id );

TO BE
$css_file = new Elementor\Core\Files\CSS\Post( $template_id );