[Solved]
This issue is solved.
For some reason, I was using "sandbox" credentials for the "live".
[Original issue]
I have created a valid API Signature on paypal.com "Account Settings" page to use NVP/API.
I can use the api but only for "sandbox" URL (https://api-3t.sandbox.paypal.com/nvp).
If I call the "live" URL (https://api-3t.paypal.com/nvp) I have an error for wrong credentials.
In the "Account Settings" page it does not allow to select "live" or "sandbox".
How can I create a "live" API account ?
