freemius-wp-sdk-license-changes-hook.php

<?php
function my_after_license_change( $change, $current_plan ) {
    switch ( $change ) {
        case 'activated':
            // License activated.
            break;
        case 'cancelled':
            // License cancelled.
            break;
        case 'changed':
            // Plan changed.
            break;
        case 'downgrade':
            // Plan downgraded to free.
            break;
        case 'expired':
            // License expired.
            break;
        case 'trial_expired':
            // Trial expired.
            break;
        case 'upgraded':
            // Plan upgrade.
            break;
    }
}

my_fs()->add_action( 'after_license_change', 'my_after_license_change', 10, 2 );