To activate the extension locate the config at: System > Configuration > Magmodules > Auto Invoice.
1. Activate the extension
Paste the obtained key in the field "License Key" and save config.
After saving, the message "Valid License Key" (in green) should be visible under the license key field. If it displays a "Invalid license key" message in red, please check if the value in the Server Name field matched the one used when purchasing the extension.
If there is a mismatch, please check your user account and the "my license keys" tab to check if the base-url is matching your license-key. If you have an staging or development domain and you need an optional license key for that specific domain you can also generate this easily in your account dashboard.
Note: If you wish to de-activate the extension on a store review, make sure to activate the extension on the main store view.