Wp_user_query search by meta_key not returning any results

You’re setting two different meta_key fields to check on: 'course', and 'clinic'. Try doing it with just one like so:

$args = array(
    'orderby' => 'display_name',
    'fields'  => 'all',
    'search'  => $search,
    'meta_query' => array(
            array(
                'key'     => 'clinic',
                'value'   => $search,
                'compare' => 'LIKE'
            )
    )
 );

What your current query is doing is returning users who match the $search parameter on the basic user columns AND the meta key “clinic”. Is this your intention?

Update 3/24/16:

Try this:

$args = array(
    'orderby'    => 'display_name',
    'fields'     => 'all',    
    'search'     => $search,
    'meta_query' => array(
        'relation' => 'OR',
            array(
                'key'     => 'course',
                'value'   => $search,
                'compare' => 'LIKE'
            ),
            array(
                'key'     => 'clinic',
                'value'   => $search,
                'compare' => 'LIKE'
            )
    )
);