OpenCart - downloadable products with options

I have updated from ver. 1.5x to 2.x in OpenCart. I sell downloadable sheet music for the guitar. Each score comes in up to 8 different versions like:
Product: Fernando Sor op1
Choises: score, tab, iPad, etc. (up to eight versions)
Customers check the versions they want to download. After they have paid, they can immediately download their selected product.

Before the update, it worked (using a vqmod module). Now after the update using an ocmod theme it doesn't work anymore. I can't even get the standard OpenCart download working. Purchased products will not show up as downloads in the "My account".

I need help to get this functionality up and to run as soon as possible.

Clip 1 shows the customers view. Immediately after the payment is accepted, the customer should be able to download from the download area in the "my account" menu.

Clip 2 demonstrate how I create different sets of options. Under the "Pick your version" I have defined the options shown in clip 1.

Clip 3: I used to have a column here all the downloads. I choose the appropriate download for each option.