This is a new ShopSite Manager that I just set up. Everything is working properly except the checkout. I'm using the Authorize.Net payment gateway. I have configured it properly using the API Login ID and Transaction Key. However, each time I complete the checkout process on the last page after the credit card information has been entered I get an Internal Server Error.
I have already verified the correct information with Authorize.Net as well as checked the checkout process without using Authorize.Net. When processing without the gateway orders go through. But I need to use the Authorize.Net gateway.
This is a dedicated server running Plesk 8 on Linux. Any help would be greatly appreciated. Thank you!