Note I am using Classic API because I am in a country where I can't use the REST API for credit card payments.
I am just getting started on setting up an application to use Express Checkout instead of Payment Standard and I'm totally lost with PayPal's API set-up. They made it incredibly difficult even reading the documentation.
I did the following already:
Set up a Classic API account for my "App" and got:
Sandbox ID: APP-XXXXXXXXXXXXX
Live App ID: APP-XXXXXXXXXXXXX
Generated API Signature in my Premier account and got:
Credential: API Signature
API Username : name_api1.domain.com
API Password: XXXXXXXXXXXX
Signature: (Really long string)
Now, I figured out that I can call this to create a test token like this:
curl -s --insecure https://api-3t.sandbox.paypal.com/nvp
-d "USER=platfo_1255077030_biz_api1.gmail.com&
PWD=1255077037&
SIGNATURE=Abg0gYcQyxQvnf2HDJkKtA-p6pqhA1k-KTYE0Gcy1diujFio4io5Vqjf&
METHOD=SetExpressCheckout&
VERSION=78&
PAYMENTREQUEST_0_PAYMENTACTION=SALE&
PAYMENTREQUEST_0_AMT=19&
PAYMENTREQUEST_0_CURRENCYCODE=USD&
cancelUrl=http://www.example.com/cancel.html&
returnUrl=http://www.example.com/success.html
But how do I call it with my own API username and password? I tried replacing my info with the PWD and the USER and it's not working.
Do I always test with the above cURL request while in sandbox? Or should I be using my own? If so, how? And what is the Sandbox ID for? I can't seem to specify it anywhere in the cURL.
I checked the documentation at https://developer.paypal.com/docs/classic/products/#ec but it doesn't make any sense.
They have a lot of documentation, yes, but what exactly doesn't make sense about it? Are you starting with the Get Started material, reading all the way through it, and then proceeding to the more detailed docs about the API calls, or are you skipping some of that?
Express Checkout does not require the App ID, so you don't need to worry about that. That would be for if you ever need to use the Adaptive Payments APIs in the future.
You say the sample they provide is working, but then you try your own credentials and "it's not working." That is not nearly enough information for anybody to help you with. Do you get an error code? Is it the security header invalid error, by chance, or what is it?
Are you working with PHP by chance? If so, check out this library. It'll make everything much easier for you.
Get me some of the details and then I'll update this answer (with an actual answer). This was all too long for a comment.