On Windows (only), the Cinema 4D Quickstart is not loading but showing a “File not found” error.

This issue was fixed in Cinema 4D 2023.1.3.

Please see: Cinema 4D 2023.1.2 - December 7, 2022 /Cinema 4D 2023.1.3 - December 14, 2022 

This occurs in most Windows installations of R26 and later which use the Webview2 (Edge) component instead of Webview/Trident/IE.

This issue is under investigation, but appears to be related to an update Microsoft issued to the WebView2 component Dec 8 causing the URL to not resolve properly.

Currently the only mitigation is to disable the Quickstart (Edit-Preferences-Communication-Quick Start Dialog Enabled at Startup). That solution is available to commercial subscribers, though trial, student and other license types do not offer the option to hide the Quick Start.