Get all custom posts with a certain taxonomy

The proper argument to your tax query is terms, not term. You can see this in one of the examples in the Codex:

$args = array(
    'post_type' => 'post',
    'tax_query' => array(
        array(
            'taxonomy' => 'people',
            'field'    => 'slug',
            'terms'    => 'bob',
        ),
    ),
);
$query = new WP_Query( $args );

https://codex.wordpress.org/Class_Reference/WP_Query#Taxonomy_Parameters

Assuming that your post types, and taxonomies are what they appear to be, and the slugs are correct, with that change your code should work.