Help with "Failure to Prepare Payment"?

[wonderz1]

Is anyone familiar with the "Failure to Prepare Payment' error? (see the red section in the screenshot below) 

We've just implemented a DonorBox to collect donations for our Covid response, using Paypal as the payment processor. One test donation went through, no problem. Others get a "failure to prepare payment" error just after they enter their address, before they can get to any options of payment method.

We thought it had to do with the country that the donor selected in their address, but I can't replicate it consistently. Sample attempts have been made from South Africa, and two different locations in the US. Only one US instance is working. 

We've used something similar using Stripe as the processor on our site for months without error. Stripe doesn't work with South African banks, so we have to move to Paypal. Any thoughts on what's going wrong? Thank you SO much for your help. 

[greenreleaf]

Same here. Then I tried again, it seemed to have gone in as my email indicated the payment. However the paypal page says its an error - return to merchant. Scary !