If SmartScreen isn't working, follow these steps to ensure it is active: Open the Start Menu and click the Settings gear icon.

Under the Reputation-based protection section, click on Reputation-based protection settings. Ensure the Check apps and files toggle is turned On.

In some cases, users find they cannot turn SmartScreen on because the settings are grayed out. This usually happens for one of two reasons:

By ensuring your Windows 10 system is fully updated through Windows Update, you will always have the latest version of SmartScreen without ever needing to perform a manual download.

If you are looking to "download" it because it seems to be missing or disabled, you actually just need to toggle it back on within your system settings. How to Enable SmartScreen on Windows 10