Make sure "Random Hardware Addresses" is turned off in Windows settings.

Hello gatlas,

If you encounter Error (-9) Invalid host when applying a Mathcad Prime license and notice that the reported HOST ID keeps changing, check whether Random Hardware Addresses is enabled in Windows.

Mathcad licensing relies on a consistent network adapter MAC address to generate and validate the HOST ID. When Random Hardware Addresses is turned on, Windows can present different MAC addresses, causing the HOST ID to change and preventing the license from being validated.

To resolve the issue:

Open Settings > Network & Internet > Wi-Fi.
Select your Wi-Fi network.
Ensure Random Hardware Addresses is turned Off.

For additional information, refer to Article CS418996 – Error "(-9) Invalid host" reported when applying license to Mathcad Prime 10.0.