Digital Downloads

It worked well for over a year, but now it hardly works. My store sells digital tutorials, now customers are complaining that they can't get the file. I am posting this manually but it does so many times. I now need to explain to everyone why they cannot download their files ... I see that many have encountered this problem and it has not been resolved. I used the Shopify store because they promised that I could use digital downloads. now I can't use it ... I found other apps, they are paid and now I have to pay almost 50 dollars a month for this ... I'm very disappointed ...