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last updated: 2016-12
If you do not have internet access on the machine you're trying to activate, you will need to contact Xamarin Support with details of your machine. You can then obtain a license file via your Xamarin store account, provided you have purchased a license.
If you login to https://store.xamarin.com/account/my/subscription/computers and click License next to the machine, you'll get a link to download the license file.
Offline Activation on Windows
After obtaining a monoandroid.licx file, it must be placed in the appropriate directory. Create the directory %ProgramData%\Mono for Android\License, and place the monoandroid.licx file into that directory (thus creating the file e.g. C:\ProgramData\Mono for Android\License\monoandroid.licx). Once this file has been created, you should be able to use Xamarin.Android normally.
Trial licenses have the word trial embedded in the filename, eg. monoandroid.trial.licx, but otherwise the instructions are the same.
Offline Activation on Mac OS X
When you receive your license file, you should save it to the $HOME/Library/MonoAndroid folder, creating the file $HOME/Library/MonoAndroid/License.
Trial licenses have the word trial added to the filename, eg. License.trial, but otherwise the instructions are the same. Once the license has been saved to disk, Xamarin.Android installation and activation should complete successfully.