No package file found

I also encountered this issue and have a workaround, although I suspect ultimately there is a small bug in the plugin (regardless I am very appreciative of this wonderful plugin).

When I exported the package on my Mac (running WP on MAMP), the package was saved as a folder containing all the data files. The important thing to note is the output was not a zip file, therefore differs from the tutorial video. I think this is where the bug is.
Then when I tried to import the package on my PC (running WP on WAMP), it also reported the same error:

[Pass] is Writable
[Fail]Contains only one Zip file.
Result = No package file found

The Import function actually expects the exported file as a zip file, not expanded as a folder.
The workaround was to zip the content of the folder into a zip file, then leaving only the zip file and installer.php in the WP directory which allowed the import to complete successfully.

Also note you must zip only the CONTENT of the exported folder, you must not include the parent folder itself. Otherwise you will get another error during the import process.

So I know this post has been marked as resolved, but I came upon the same problem and just checked, ran a search and only found one .zip file in my directory (the one from the package file). If it’s any help, aside from what people posted above is also says at the bottom “Note: Manual extraction still requires the package.zip file “

Thanks!