Downgrade 2025 RDS cals from CSP to 2016

Hi Loyiso,

First, it’s important to note that CSP RDS CALs do not provide a separate downgrade key for older versions; instead, downgrade rights are automatically included in the entitlement. This means you will still install the 2025 CALs, but your RDS Licensing Server will allow them to be applied to an RDS 2016 environment as long as downgrade rights are recognized.

To begin, please open Remote Desktop Licensing Manager, right click your licensing server, and select Install Licenses. When prompted for the License Program, select Service Provider License Agreement / CSP. Enter the license pack information exactly as provided by your CSP reseller. At this stage, the Licensing Manager may show an option indicating “This license supports downgrade rights”, which confirms compatibility with older RDS versions such as 2019, 2016, and 2012 R2.

If your server is trying to use the automated phone Clearinghouse and not completing activation, choose “Web Browser” as your activation method instead of “Telephone”. The Clearinghouse phone system does not support CSP license activation, so the web method is required. After activation, the license server becomes aware of the version flexible rights included with CSP RDS CALs and will issue CALs to Windows Server 2016 session hosts without additional steps.

If the license server still fails to activate the pack, please ensure the server is fully updated, the Remote Desktop Licensing role service is properly installed, and no proxy/firewall is blocking outbound HTTPS traffic. In some cases, reactivating the licensing server (right-click → Activate Server) resolves CSP recognition issues.

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