My curve blu card has been declined at Aldi, Iceland and First Group buses in the last week. I have plenty of cash available on the card that curve is connected to on my mobile, indeed I used the card that curve is connected to at all 3 of the listed places where curve was declined. At this rate it is not going to be worth having if I cannot trust it.
Please contact customer services and they will be able to tell you the reason for your declines. As we are users like yourself we don’t have that kind of information to hand.