I can confirm having same issue with coinbase. All went well when prices were up and I bought with couple hundred of euro an amount of bitcoin from coinbase. I used direct payment costing me a few percent. As soon as the market slumped my subsequent payment got rejected after the transaction was marked as done on bitcoin. I called my bank. They told me they never received any request from anyone and therefore I know that the coinbase site never attempted to write any money from my card with that transaction. I tried again the same day and then again but same result. First it looks like I purchased the bitcoin but an hour later it is rejected and the bank never even got a ping or attempt to take it off the card. The card is fully functional and authorised. Coinbase had the audacity to come with following explenation: it must be your browser. Well the browser does not reject a transaction that went through the coinbase system and then forgot to take it off the card of course the price is up now so too late to buy bitcoin. Anyways I used two browsers that day and both same.