I fixed this outside of Wappler by creating a new app with Cordova in the CLI, then following up on the almost never-ending error messages and solutions at stackoverflow.com. It took several hours to finally get there.
Now within Wappler I can create, build and emulate the app for Android. Phew! 
Next I need to find out how to create an app for iOS. Presumably Iād have to copy the entire project from Windows over to a real Mac and build the IPA file in Terminal/Xcode? 