AbleCommerce Shopping Cart Software

Hi, I have added the volume discount, buy at least 2, save $4.00 each for example. The shipping method is UPS (Free for $100+ orders). When the Subtotal is less than $100 (ex. product total $110, discount -$20), the shipping rate $6 should be applied. Everything is calculating correctly until the ch...

This is the error log I found. [*]ERROR 2010-07-12 15:59:02,160 11570399ms Object a - An error occurred during the checkout process. The checkout has failed 3 times and will NOT BE attempted again. UserId: 13093150 / 9badc2b5-f192-471c-bc50-7aa81289b0c5 Customer: / / System.Data.SqlClient.SqlExcepti...

I'm trying to convert the basket into the order with a custom payment method.
However, the checkoutresponse.success is false. Is there anyway I can see which part is failed?

For the custom payment method, I only create a new method without assigning a gateway.
Is it an issue in this case?

After adding the checkout by Amazon feature in AbleCommerce, how to move basket to order while receiving amazon order notification?
We would like to do this the same way as checkout in AC.