Can't authorize Card to Top-up


I am using an Android Phone and I have just downloaded the app. When trying to top-up using a UK credit card, the app lets me enter in all the data about the card, and then tells me authorization is in progress and that 3DSecure details may be asked. Then, no 3D secure, but simply a message stating that the card could not be authorized.

Why is this happening and how do I solve it?