I tried with the new version, and it did not work. But since I am trying to eval DF for a smallish project, now I was a bit more determined to find out what was going on...
After 8 attempts to install v2.2.0-0 and import apps, with slightly different circumstances (different machines, browsers, Windows versions...), I found out what the issue was.
If you install to directory d:\Program Files\dreamfactory-2.2.0-0\ it will NOT work.
If you install to directory c:\Bitnami\dreamfactory-2.2.0-0\ (initially offered) it will work.
(There were no access restrictions to any directories, no firewalls, port conflicts, or other funny env circumstances, of course.)
The most sane idea is that the problem is presence of spaces in the root DF path.
So, I suggest:
1) fix this, it must be a 30 seconds touch. But the second one is way more important:
2) The error log said nothing about failure to import an app, so increase logging verbosity a lot, and I do not only refer to app import, but wherever needed. It will make possible more effective methods of identification of issues to be used, instead of banal and painstaking trial-and-error.