Hello, @munayam I am also facing the same issue. I can not update the course. I have tested on different hosting and localhost.
You can test yourself-
Install Fresh WordPress
install Tutor LMS
Create a new Course then click on the publish button. Then you will see the issue.
Here is the error code:
Fatal error: Uncaught TypeError: Argument 1 passed to TUTOR\Input::sanitize_array() must be of the type array, null given, called in C:\xampp\htdocs\tutor\wp-content\plugins\tutor\classes\Course.php on line 544 and defined in C:\xampp\htdocs\tutor\wp-content\plugins\tutor\classes\Input.php:252 Stack trace: #0 C:\xampp\htdocs\tutor\wp-content\plugins\tutor\classes\Course.php(544): TUTOR\Input::sanitize_array(NULL, Array, true) #1 C:\xampp\htdocs\tutor\wp-includes\class-wp-hook.php(310): TUTOR\Course->save_course_meta(8, Object(WP_Post)) #2 C:\xampp\htdocs\tutor\wp-includes\class-wp-hook.php(332): WP_Hook->apply_filters('', Array) #3 C:\xampp\htdocs\tutor\wp-includes\plugin.php(517): WP_Hook->do_action(Array) #4 C:\xampp\htdocs\tutor\wp-includes\post.php(4706): do_action('save_post_cours...', 8, Object(WP_Post), true) #5 C:\xampp\htdocs\tutor\wp-includes\post.php(4819): wp_insert_post(Array, false, true) #6 C:\xampp\htdocs\tutor\wp-admin\includes\post.php(426): wp_update_post(Array) #7 C:\xampp\htdocs\tutor\wp-admin\post.ph in C:\xampp\htdocs\tutor\wp-content\plugins\tutor\classes\Input.php on line 252