Can’t buy credits…don’t know why

I downloaded the app, then tried to buy a credit pack; selected the $2.99 pack. The little spinning wheel in the center of the screen spins for a while, the stops. No credits purchased. Useless program if you can’t buy credits to pay for a faxed page.

yachtsman14580 about Send & Receive Fax App- iFax, v3.9