The Add to Cart button is disabled and not working when there is only 1 item left in inventory. I have changed the "if( !$this->in_stock( 1, true )" to "if( !$this->in_stock( 0, true )" on line 1105 of the mp_class_product.php file and all is well. I can see where companies with large item inventories may not want to sell a product when the inventory indicates there is only 1 left but the store I working on is almost all 1 off products. I suggest adding a variable to allow this to be changed when the function is called.
Dominant Domains LLC.