*Shortcodes are case-sensitive*, so you should:

* Use `[Edit_field Field="Email_1"]`

* And *not* `[Edit_Field Field="Email_1"]`

Because you defined the shortcode as `add_shortcode('Edit_field', 'Edit_field');` — note the first `Edit_field`, where the `f` is in lowercase.

Secondly, *WordPress converts the shortcode attributes to **lowercase***, so the `$Field` in your case will be undefined and therefore, you should use `$field` instead.

However, please just avoid using `extract()` and use the `$atts` instead to access the shortcode attributes:

```php
function Edit_field( $atts ) {
	$atts = shortcode_atts( array(
		'field' => '',
	), $atts );

	if ( $atts['field'] == 'Email_1' ) {
		return $_POST['Edit_Email_1'] ?? 'NA';
	}

	if ( $atts['field'] == 'Client_Description' ) {
		return $_POST['Edit_Client_Description'] ?? 'NA';
	}
}
```

Additionally, always check if the POST variable is actually set:

```php
// Example for the Edit_Email_1 variable:
return isset( $_POST['Edit_Email_1'] ) ? $_POST['Edit_Email_1'] : 'NA'; // use this
return $_POST['Edit_Email_1'] ?? 'NA'; // or like I used in the above function, using PHP 7 format
```