Corona Simulator uses Apple’s Application Loader utility to validate and submit your app to the Mac App Store.
If you get a hard-to-understand error in the Send to Mac App Store part of the build the best thing to do is to run Application Loader by hand and figure out the issue from there (it will either be a problem with Corona’s integration of Application Loader which we can address or an Application Loader issue which you would have to take up with Apple; let us know either way so we can smooth the way for others).
First, build your OS X app in Corona Simulator, choosing Send to Mac App Store and get to the point the error occurs.
Second, you need to run Application Loader which is most easily done by running Xcode and then choosing the menu option:
Xcode > Open Developer Tool > Application Loader
Once Application Loader is running, click on the Choose button in the bottom right corner of the window (there are several ways to open things in Application Loader but this is the only one that will open a package). Navigate to the Save to folder you specified when you built your app and choose the <appname>.pkg file you find there.
Application Loader will do its thing and hopefully the issue will become more apparent. At this point you may need to search for things on the internet to find possible solutions to your dilemma or inform us of a bug that results in apps being built that Application Loader wont work with.