I'm afraid the images in your last message are coming through as broken images, so I can't see the issue in Visual Studio. Could you please check and reference the images again?
However, are you able to set the site up in IIS, then run it from a localhost port.
Open the website/solution in Visual Studio then attach to the w3wp.exe worker process.
My feeling is that one of two things might be happening:
- There is a client side error which could be killing the postback; or
- In the code-behind event for the button click, some error is occurring (though you did mention there is nothing in the event logs)
Has this project been customised, particularly the E-Commerce functionality?