Can’t download books – Free Books Pro- 23,469 classics for less than a cup of coffee. Review

Every time I try to download a book I get a message saying that my 3G is disabled for downloading. I do not have 3G I have 4G and is not disabled for free books I made sure of that so what’s going on I’ve wasted $.99 on an app I cannot use please fix or advise thank you. I have a 2016 iPad air 2
Review by The Elves on Free Books Pro- 23,469 classics for less than a cup of coffee..