Hi, after a lot of struggling I was able to renew my Pro account for a year. There were two parts to the problem.
The worst part was that DigitalRiver requires you to accept third-party cookies. If you don't accept them by default, the credit form does nothing to tell you it has a problem. If your customer is not a web developer, you have probably lost them at this point.
The second problem is that even if you grind your way through payment, you still get notified by Flickr's account page that you are on a monthly payment plan, even though you started the whole journey by selecting the yearly plan.
I really like Flickr as a service and hope it sticks around for a long time. I know you are probably short-staffed, but I think it is important for you to prioritize making it much easier for customers to give you money.