If you want to show on increase or decrease the quantity of items than use this function
function remove_disable_updatecart() {
?>
<script type=’text/javascript’>
jQuery(document).ready(function() {
jQuery( ‘.shop_table.cart’ ).closest( ‘form’ ).find( ‘input[name=”update_cart”]’ ).removeProp( ‘disabled’);
});
</script>
<script type=”text/javascript”>
jQuery(document).on(“click”,”.reduced.items-count”,function () {
jQuery( ‘.shop_table.cart’ ).closest( ‘form’ ).find( ‘input[name=”update_cart”]’ ).removeProp( ‘disabled’);
});
jQuery(document).on(“click”,”.increase.items-count”,function () {
jQuery( ‘.shop_table.cart’ ).closest( ‘form’ ).find( ‘input[name=”update_cart”]’ ).removeProp( ‘disabled’);
});
</script>
<?php
}
add_action( ‘wp_footer’, ‘remove_disable_updatecart’, 99 );
?>
and please make sure the <?php ?> tags are right otherwise its not working