Plugin doesn’t send invoice to customer?!

Hello,
I’m interested in buying your plugin but I encounter a problem.
The invoice is not sent to the customer email, but to the seller email.
Another way for the customer to get his invoice after the transaction’s summary , is to perform an action to download it.
I’m searching for a plugin that automatically sends it to the customer email.
Can you help me setting your plugin to do this?
Best regards,