I think that the error log request nailed it. As the 1.2.10 is not yet public, but being developed it seems that AbanteCart import utility does a domain check and fails.
Accessing store with non-configured or unknown domain.
The problem is that I don't want to go live before its done just to import some changes. Perhaps the developers can remove the need for a check and just import the file to where it came from, just checking the database name to assure that it's before restored to where it came from? On the other hand, as the import is from the work-in-progress site, where else can the data be uploaded to?