If you are having trouble with your API account, please first try the API test page.
Enter your payment email address and your provided API key, and the page will run a real test query using your account.
If the results come back OK, then it indicates there is either a problem with either the script or the server configuration.
Here are some common issues and their solutions:
cURL used in script but not installed on the server
Incorrect headers sent to API (usually shown as a "Bad Request")
cURL usually sends headers automatically. If you are manually setting them, try removing this code altogether and see if it handles it by itself. If this doesn't work, make sure you are sending Content-Type "text/plain" and the correct Content-Length