checkout not working with iPad

A gal visited our website, clicked the Easy Digital Download “add to cart” button but when she goes to the checkout view, nothing happens. She said this happens when she is using her iPad but not when she is on her mobile or personal computer. What could be causing this iPad issue? What should I tell her to do to fix the problem?

https://www.ads-software.com/extend/plugins/easy-digital-downloads/