Exclude a category from WP_Query

I’ve been banging my head against the wall for last couple of days trying to exclude a category from an archive of easy digital downloads, which i am displaying in a custom widget, however i cannot hide a category called ‘custom-project’ no matter what i try.

This is the code i am trying to use, based on instructions from https://codex.wordpress.org/Class_Reference/WP_Query

$argsQuery = array(
    'posts_per_page' => 3,
    'post_type' => 'download',
    'tax_query' => array(
        array(
            'taxonomy' => 'download_category',
            'field' => 'slug',
            'terms' => 'custom-project',
            'include_children' => true,
            'operator' => 'NOT_IN'
        )
    ),
);
$get_latest_downloads = new WP_Query( $argsQuery );                         
$i=1;
while ( $get_latest_downloads->have_posts() ) : $get_latest_downloads->the_post();

//WIDGET BODY CODE

$i++;
endwhile;

I also tried using ‘cat’ instead of ‘tax_query’, but with no success as the category ‘custom-project’ is still displaying inside the loop of posts.

$argsQuery = array(
    'posts_per_page' => 3,
    'post_type' => 'download',
    'cat' => '-5',
);
$get_latest_downloads = new WP_Query( $argsQuery );                         
$i=1;
while ( $get_latest_downloads->have_posts() ) : $get_latest_downloads->the_post();

//WIDGET BODY CODE

$i++;
endwhile;

I am certain that slug name and category ID are correct. Any kind of help is greatly appreciated.

Issue 1

In your tax query, you should use NOT IN instead of NOT_IN. That’s preventing your tax query from working ( Assuming that the other fields are correct ).

Issue 2

In your arguments for WP_Query(), you should use category__not_in instead of cat. So, change your code to:

$argsQuery = array(
    'posts_per_page'   => 3,
    'post_type'        => 'download',
    'category__not_in' => 5 ,
);