Maybe you have to try to do things again. In the guide, you should
Open package-solution.json from the config folder. The
package-solution.json file defines the package metadata as shown in
the following code:
When this is done, run the gulp command
The command will create the package in the sharepoint folder:
So far so good, next
Upload or drag and drop the helloworld-webpart.spapp to the App
... and click Deploy.
When I do this, I get a ProductID on my dev-tenant App site, but from your screenshot I can tell that there is no ProductID, and maybe that's where things fail?
Another option, which you might have missed, is to install Drop 4 and upgrade your web parts? I had these issues doing a demo, and later on when I upgraded to Drop 4, everything worked like a charm. See Release Notes Drop 4 and MDL2 on how to upgrade your apps.