Full payment via point system doesn't generate an email with invoice

Hi,

That's not a problem to be fixed. This depends on how your shop is configured.
When you use the points to pay for the order, the total amount of the order is 0, which removes the payment method from the order.
So at the end of the checkout, the order is just created with a total amount of 0 and the default order status, which by default is "created".
So if you configured your confirmation email and PDF to be sent when the order is "confirmed" (which normally happens after a customer has paid via a payment method), it's normal that these are not sent.
The solution however is already on your website. HikaShop comes with a "validate free order" plugin that you can activate and configure via the Joomla plugins manager so that orders created with a total amount of 0 will be confirmed, which will then trigger the confirmation email and PDF to be sent to the customer.