2checkout integratio: Parameter Error

[InternetDominus]

Hi,

 

I am trying to use 2checkout for payments. I have added the vendor account number, the secret word, and at the 2checkout site I added the URL where users are supposed to be redirected after successful payment.

 

However, my problem is that I cannot even pay yet. I get a parameter error, but no more feedbak on the error page. I read somewhere at 2checkout that now for every product we sell, we must add it to our 2checkout product database. Is this the case with WHMCS? If so, how/where do I tell WHMCS the product Id I assigned to each product at 2checkout.

 

Or, am I doing something wrong?

 

thanks!