setExpressCheckout and SSL/TLS error

Question

I\'m trying to develop a simple application that will enable users to purchase services off a website through the Paypal API. This application is running on ASP.NET with C#.

Answer 1

You're probably connecting to api.paypal.com or api.sandbox.paypal.com, and not sending along your API certificate. The API certificate is a client SSL certificate used to complete the SSL chain.

If you don't have or are not using an API certificate, you should connect to api-3t.paypal.com or api-3t.sandbox.paypal.com for Live or Sandbox respectively.