Hi
With Amazon, when you initially place an order with a card, Amazon takes a small amount (£1.00) to check the card is valid. This is a common practice; Apple takes £1.58 to confirm the card exists and is active. This is usually refunded within 10 days, but if you contact the in-app support team and ask them to refund it, they would do so immediately.
If you only had just enough funds for the order, then once Amazon takes the £1 from your card, you are left with not enough for the order, and it might get cancelled.
PS. This charge is only taken when you initially set up the card with Amazon, all subsequent orders would not have this, in my experience. So if this isn’t the first transaction, then you may have a different problem. 