PayPal Payments Pro 2.0 Payflow edition causing Express Checkout to error

PayPal Payments Pro 2.0 Payflow edition. That's what they told me the current product was now called.

One tech at PayPal integration dept. told me that "it won't work with Zen-Cart. You need version 1.5 which is also confusingly called 3.0"
Yes, that is what he said.

While I was talking with PayPal, I was tinkering with the payment module settings for PayPal Express in my cart admin, and saw

PayPal Mode
Which PayPal API system should be used for processing?
Choices:
For choice #1, you need to supply API Settings above.

1. PayPal = Express Checkout with a regular PayPal account
   or
   for choices 2 & 3 you need to supply PAYFLOW settings, below (and have a Payflow account)
2. Payflow-UK = Website Payments Pro UK Payflow Edition
3. Payflow-US = Payflow Pro Gateway only

( ) PayPal
( ) Payflow-UK
( ) Payflow-US

So, because I am on the phone with PayPal setting up a 'Payflow' edition, I checked 'Payflow-US'

Well, that broke the Express Checkout with the old "Geographical region" error.

I ticked it back to "PayPal" and it all works.

Hope this saves somebody some time.

PayPal modes explained:
PayPal = PF 1.5
Payflow-UK = PF 2.0
Payflow-US = PF 3.0 (happens to also often apply to CAN and AU, and a few other countries besides just US; always changing)

These are rough matches. PayPal's implementation of which API is used "where" in the world is a constantly moving target, and they can change which PF API is linked to each merchant account. Unfortunately they never tell the merchant which one has been assigned, and so the best we can do is give more meaningful "words" to it. Hence the way the "modes" are listed in the module.