PCI security error with my paypal pro: security header is not valid

Hi 

I have imbedded a payment form to my website and a t the time to submit the payment it comes with the following error message.

PCI security error

security header is not valid

I have paypal pro and have use the number on the form. 

Can you help please

Thanks 

Maria

The probable reason for this error is when we enter incorrect credentials. Could you please recheck your API username and API password.

Reference guide: https://developer.paypal.com/docs/classic/api/apiCredentials/#creating-classic-api-credentials

https://www.jotform.com/help/458-How-to-Integrate-Form-with-Paypal-Pro