您无权进行此API调用？ Paypal与Ci-merchant

I know this question has been asked a lot but none of the answers to those questions are helping me. I am using Ci-Merchant to make paypal Express Checkout transcation. The problem is that every time I make a transcation, the status is returned with failed and a message saying "You do not have permissions to make this API call". My credentials are all ok and I am using both test and live accounts and taking care of the test and live parameter. Any Thought on it? Thanks in Advance

This error can be multiple things. You'll want to send us some more data on your doExpresscheckout api so we can see what you're actually passing. But to start with, are you testing in the live or test environment? As Andrew stated you'll want to begin with the paypal account and the look over some of the following:

1. Is the email address on the account confirmed
2. Is the PayPal account a business account? If not, upgrade it
3. If you're testing a transaction in TEST MODE a. Use Sandbox API creds If You're testing in LIVE mode a. Make sure you're turn Mode = LIVE (usually a toggle) on the cart end b. Make sure to use API creeds from business account b. are they giving you an endpoint path and port options for Express Checkout?
4. As you can see it could be a compilation of things
5. Are you trying to run a transactions from an older order? a. this api call would denote a reference transaction which is permission based
6. https://ppmts.custhelp.com/app/answers/list/kw/You%20do%20not%20have%20permissions%20to%20make%20this%20API%20call/sno/1/search/1/session/L3RpbWUvMTQwMzg0MzEyNS9zaWQvelRuZVBRWGw%3D