Although all tests have gone through fine in the Sandbox mode, after switching to Live mode today, I get an error saying (CODE)520003 Authentication failed. API credentials are incorrect.
However, I have copy-pasted the details ten times already - even checking them character by character to see that they match. The account has been approved by Paypal as a Business account. I am using the advanced payments of the plugin.
This is urgent, and I cannot stress enough the importance of getting this to work, for my client. If not the API credentials work, what can I do? Is there a way to regenerate them? Or is there a way to see more specific error messages?