There are several things to check with regards to Lightworks not starting:
1. Make sure you are running the latest version of Lightworks (2021.2 or higher) from the Downloads page.
2.That the graphics card drivers are installed and working correctly. Please make sure that a "standard VGA" driver is NOT installed.
3. That the sound card is installed and working correctly, ie, you can hear audio coming from the system. Please make sure that speakers/headphones are connected and that the audio is enabled.
4. Intel 945/G33/G31 graphics chipsets are no longer supported. If you have one of these graphics cards, please upgrade it to resolve this issue.
5. That your DirectX is up to date. Please download the DirectX End-User Runtime Web Installer from here: https://www.microsoft.com/en-us/download/details.aspx?id=35
6. If you are running Windows Defender, please disable it and reinstall Lightworks.