Sandbox issues
The sandbox site seems riddled with errors that prevent you actually using it. I had to resort to using the LIVE site to test my application - but that means I'm incurring charges to list items - items I immediately remove because I actually have no intention of selling those items... that's because I'm just a software developer working on an integration for my clients. The sandbox should be a working and usable environment.
I doubt anybody from ebay will actually everr see this or bother trying to rectify it, but in the vague hope they do, the main issues are:
1. You can't publish an offer via the API without setting the various business policies.
2. But you can't create those policies because the site has loads of problems:
2a. Try to create a shipping policy and the page doesn't load
Error message:
There was a problem with business policies
We ran into a problem. Please try again. If the issue persists, please review our help site to contact customer service.
2b. Try to create a payment policy and it doesn't let you save it
Error message:
Please provide the correct information in the highlighted fields
Provide a payment method
PayPal is required