Hello LLW,
The warnings you note are coming directly from eBay's API and we have no control over the API responses. We are not aware of the difficulty you have described and will need to look into this further.
eBay has not made options for Managed Payments available via the API which listings go through when they are submit from a third party service such as ours. As such, we currently do not have the means to make an option for Managed Payments available in the Checkout section of the listing creation page; eBay must make the option available in the API for us to be able to accommodate it.
In order for us to look into this further, please file a support case with us from under the Help tab letting us know a few example item numbers for active listings where you have posted to eBay US and other eBay sites where the listings are not available for purchase on the other sites - or if you have utilized an eBay service that includes posting to multiple sites, please include that information in your support case so we can look into this further.
- Craig