Check your API version in module backend, it should be API version: V11.
Check the credentials using in FirstData configuration.
If you are not able to fix the problem, fill our below support form http://www.modulebazaar.com/support
Go to PayPal Profile page.
Click Website Payment Preferences.
Configure, Auto Return for Website Payments and Payment Data Transfer (optional) and Encrypted Website Payments
After completing this configuration, Identity Token will be generated and will be displayed in Payment Data Transfer section.
Our module works with default theme, for customized theme it should work. Kindly purchase the module, you have 15day money back guarentee. If you are not satisfied, you can opt for refund.