I need a sharp experience magento developer to find out & fix auto key assignment to byers after auto invoicing through paypal payment.

I have a very specific requirement for my magento site, 99% of the work is done. It is a totally custom built module to perform some stuffs. The main reason we are posting because developer has left the company without completing his job. I know magento does auto invoicing but here our problem is very specific, the system is supposed to assign some keys to each of the byers after the invoice generation. Even it is working correctly from the admin side invoice generation, the problem is happening when somebody is paying from paypal and after payment it is supposed to generate the invoice automatically, but here the invoice is generating automatically but no key is getting assigned. I need a sharp experience magento developer to find out the cause by analyzing the system and make it happen the auto invoice generation after successful payment from paypal along with assigning the keys to the particular byer and all other stuffs it is supposed to do, IT is a very small project and my time is limited to 3 days. I need someone to look through the project and fix it. My maximum budget is 50 USD so bid it accordingly. I would pay only after successful checking of the site. All the details would be given to the selected bidders. There are more works to come, if you have proven skills then it would be a golden opportunity for you to be in our team. Inviting bids from individuals, companies or teams.