You don't need to add the license to the MX, you just need to have a valid license. "Customers are expected to have a valid AnyConnect license to use AnyConnect with the MX Appliance. Customers are not required to validate their licenses via the Meraki MX or the dashboard. Customers will only be required to accept terms and conditions of use before they can enable AnyConnect. If you are already using AnyConnect or setting it up for the first time, there will be a dashboard notification to accept the terms and conditions of use. There will be no disruption of the AnyConnect service for active networks." https://documentation.meraki.com/MX/AnyConnect_on_the_MX_Appliance/AnyConnect_Licensing_on_the_MX
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