I got this problem not only in Windows, also in Mac. Update for mac users using macOS Sierra 10.12.6 and Android Studio for Mac 2.3.3 Now execute the command sudo ionic emulate android it will run correctly Just before running the command sudo ionic emulate android go to the Android Studio open the AVD Manager then create AVD(if not yet created) and launch it in the emulator.
Create your emulator and try ionic emulate android again