WordPress meta_query not working

I am having issues with a meta query on a custom post type.

The following arguments are set:

$args = array(
        'post_type'     => 'wp_comp_entries',
        'posts_per_page' => -1,
        'meta_query' => array(
            'relation' => 'AND',
            array(
                'key'     => 'wp_comp_entry_competition-id',
                'value'   => $_POST['competition-id'],
                'compare' => '=',
            ),
            array(
                'key'     => 'wp_comp_entry_email',
                'value'   => $_POST['email'],
                'compare' => '=',
            ),
        ),
    );

A print_r of this looks like:

Array
(
    [post_type] => wp_comp_entries
    [posts_per_page] => -1
    [meta_query] => Array
        (
            [relation] => AND
            [0] => Array
                (
                    [key] => wp_comp_entry_competition-id
                    [value] => 972
                    [compare] => =
                )

            [1] => Array
                (
                    [key] => wp_comp_entry_email
                    [value] => example@example.com
                    [compare] => =
                )

        )

)

Which is great. I then run

$lookup = new WP_Query( $args );

The start of a print_r of $lookup looks like:

WP_Query Object
(
    [query_vars] => Array
        (
            [post_type] => wp_comp_entries
            [posts_per_page] => -1
            [meta_query] => Array
                (
                )

As you can see the meta_query is empty. I have no idea what is causing this as at the bottom of that dump there is this:

[query] => Array
(
    [post_type] => wp_comp_entries
    [posts_per_page] => -1
    [meta_query] => Array
        (
            [relation] => AND
            [0] => Array
                (
                    [key] => wp_comp_entry_competition-id
                    [value] => 972
                    [compare] => =
                )

            [1] => Array
                (
                    [key] => wp_comp_entry_email
                    [value] => example@example.com
                    [compare] => =
                )

        )

)

Which shows that my code is recognised, WP just isn’t feeding it into it’s query. I am lost and looking for any direction on why this could not be working?

– EDIT –

I must add I have tried the standard query from the Codex with no joy either.