Customer is not able to download a product after purchase

I use zen cart 1.5.1 with ccavenue for payment gateway and zone rates for shipping.

Under the category ebook I sell downloadable books. Our ccavenue used to crash without a shipping address so I used to fool it by giving a very small weight and setting shipping for that weight to zero. However my problem is that customer is not able to see the download link after purchase. I have read the forum again and again seen video etc. But I must be doing something wrong that customer is not able to download the product. Currently there an ebook called "Day by day with Bhagavan". Which has the settings as shown in screen shot. Can you help me find the error? I am adding two screen shots for the product. Everything works OK except the customer is not getting the download link. I have set the weight for this product to zero

And when you go to the Attributes Controller ... and look at this Product you see the green dot next to the filename, correct?

Is the filename a Zip file?

What is the size, number of days and download attempts that you have set on the Attribute?

Yes I see green light. The file name is "daybyday.zip" The number of days is 7 and the number of downloads two.

I have sent the details via PM to you.

The size of the file is 817 KB