A Unity ID allows you to buy and/or subscribe to Unity products and services, shop in the Asset Store and participate in the Unity community.
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I had to get the android sdk manager to download a new set of the build tools (20.0) as there wasn't a zipalign anywhere in the sdk folders, then...
Path variable was the problem for me, Win 8.1, jdk and anroid sdk in 64bit. None of the installers had added anything to the PATH variable....