I've just installed Sencha CMD and Sencha Touch Latest versions and try to make a new app so after "sencha generate app example ../example" I could see the results on my browse, but when I tried "sencha app build native" to se how it works on the simulator nothing happens. No errors, no messages and no Launch. I'm using Mac OS and I've already develop for iOS.
I'm not sure if you did this as you didn't mention it in your post. You need to make sure the settings in your 'packager.json' match with the setting you like. If you want to build for iOS you need to set the iOS specific parameters such as provisioning ID.