Hey @Kprime
I would recommend as you receive that specific error message about your transaction to try to follow this article for troubleshooting steps.
If you have an Android device, you can also try via the Stadia app to purchase games (once purchased, you can play them everywhere, on mobile, TV or PC). With Android you can also use PayPal or Google Play Balance as payment methods (depending on the country though, here is a list of accepted payment methods per country).
If you don't have an Android device, you need to try another credit card in the browser. There are other options like Revolut for example, which people were recommending, but you need to do some research on your own, which credit card works best for you.
You can also contact the Stadia support as they might be able to escalate this further, it would be at least worth a try.
