Wordpress Support Bug fix woocommerce

General information for the website: sell digital goods
Description of every page/module: Hi
looking for a solution to a bug i have ,
in my site kimprojects,com (shop) im about to sell digital goods . i installed a wordpress plugin that send serial numbers to every purchase of one of the apps i sell online .

(http://codecanyon.net/item/license-manager-for-woocommerce/5089794)

we discover that as long there is no file attached (downloadable file which is the product i sell ) , the buyer receive the email with all the details .
but if any downloadable file is attached the buyer doesn't receive any email.(this is email contain the detail of the transaction and also the serial number , so this is super important )

we tried making in it "virtual" and Downloadable " (both ticked ) but still no solution

i talked with the plugin owner he said that this is not the plugin fault , but the wooCommerce system. there are some bugs there .
i need this issue solve ASAP
Description of requirements/features: English Level A+
5 Stars as Seller With 10 Reviews
working skype with headset for voice call
Payment methods: Paypal
Specific technologies required: wordpress, css, html,
Extra notes: should be super fast with very good communication