Getting custom plugin or code snippet to fire.

I have club members listed in the Participants Database plugin. Members must be in the database and membership must be active before they can register (using User Registration and Membership). I have written the following code and tested it both as a plugin and code snippet. According to error logging (which for easier reading purposes I have removed from the code below), the code is not executing. What am not understanding?

Thanks.

//Verify Email Active

/* Only active members located in Participants Database can register with the  website.

 * 1) Sanitize email

 * 2) Find row in Participants Database containing sanitized email.

 * 3) If row exists, check that membership status is active.

 * 4) If row does not exist or membership status is not active, return error.

*/

function verify_custom_db_email_active ($errors, $sanitized_user_login, $user_email) {

    global $wpdb;

    $sanitized_email = sanitize_email($user_email);

    $table = $wpdb->vxj2_participants_database; 

    // Query for the email

    $row = $wpdb->get_row(

        $wpdb->prepare ("SELECT membership_status FROM $table WHERE email = %s", $sanitized_email)

    );

    if ($row) { // Check if membership is active

        if ($row->membership !== “Active”) {

            $errors->add ('membership_inactive', __('Your membership is not active.'));

        }

    }  else {  // Email not found in database

        $errors->add('email_not_found', __('Email address not found in our membership database.'));

    }

    return $errors;

}

add_filter ('registration_errors', 'verify_custom_db_email_active', 1, 3);