You might have checked this already but I found this in the manual.modernbill.com that describes the error your getting. If this doen't work I would contact Modernbill.
Q) When I try to process credit cards using Authnet in the order form, I get the following error:
An error has occurred and your order cannot be processed at this time. Please try again later. ()
1. Check to make sure you have cURL installed with Open SSL enabled. To learn more about cURL, take a look at the cURL Setup doc.
2. Go to Tools/System Config/Main System Config and make sure you have the exact location of where cURL is installed on your server entered in the Set cURL Path textbox. In most cases using PHP as the cURL path will not work.
3. Go to Tools/System Config/Authnet module settings and make sure you have both the Login ID and Password entered in the Set Your Login ID, Password textbox. They should be separated by a pipe "|" as shown below.
4. Make sure you have setup your system to accept credit cards according to the Accepting Credit Cards document.
Q) What port does your system use for Authorize.net?
A) Your system only uses SSL to connect to Authorize.net.
Q) An error has occurred and your order cannot be processed at this time. Please try again later. (Ship To First Name is required.)
A) Login to your Authorize.net control panel. Then go to Settings/Payment Form/Form Fields and uncheck required fields.
Thanks, that helped. I am now able to conntect
to authorize.net. However, I've tried several different
(of my own) cards which I know are valid, and I'm getting
a decline message each time I attempt to order...