I have been having difficulty completing transactions on Paypal. I click on the Paypal button on the merchants web page. This takes me to the Paypal login. I login and PP asks me to confirm the payment card. I do this and the card issuer (American Express) sends a verification code. I enter this and after a few seconds, I am directed back to the merchant's web page but the transaction has not happened. There is no error message and no indication why the transaction has failed. This doesn't happen all the time but only with big purchases > 100 GBP. Neither the merchant now American Express have any knowledge of why the transaction failed and no attempt is shown in their logs. I do not want to change cards since the purpose of using Paypal is to be able to charge the purchase to Amex even though the merchant does not accept Amex. The problem is on my late 2013 iMac and happens on Firefox and Safari, multiple vendors
