Why are credits being taken and nothing being generated?

I simply wanted to try out Firefly and it rejected my first two images and then it says it generated one video from a photo but could not display it so I tried it again and it told me that I had already used all my credits. I show as having 25 credits, but I have no saved video or any visual output to judge your app upon and now I’m being told I have to wait days for credits to be available again. Doubtful I’ll spend money on something that doesn’t work when you allow me to try it .