I have been trying to purchase products on my website through 2CO to verify that everything is set up ok. I have been trying to make actual payments. I am using version 2.0.25. The problems I am facing are as follows:

1) When I try with a visa card, the payment process is not completed and I remain on the 2CO page with the error saying 'Your authorization failed for the following reason:
Authorization Failed Authorization could not be obtained
Please go back and attempt to correct your information or
choose a different payment method.'

2) When I use the AMEX card, I am taken back to my website, but I get an error that says 'There has been an error processing your credit card. Please try again.' At the same time I get an email from 2CO saying that the sale has been made. But there are no updates on website backend about a confirmed order coming through..

These credit cards are fine and working otherwise. So not sure what the problem is. Kindly advise urgently as I may be losing sales because of this issue. Attaching screenshots of both issues

Thanks & Regards,