If you are seeing this when trying to use your webcam, there are a few things to check.
1. Make sure your webcam is not being used in another application.
2. Check the recorder control bar to make sure the webcam feature is turned on.
3. Check to see if your computer is running any anti-virus software such as Kasperksy, BitDefender, McAfee, Norton, etc - usually the icon will show in the bottom right of your Windows taskbar. If so, try to disable.
4. If you are using an external webcam, make sure it is properly connected to your computer (typically they plug in via a USB port).
5. Ensure you've installed the latest software for the webcam. If your webcam is built-in to your laptop, you can get the drivers from your laptop manufacturer's support site.
Logitech c920 is one of the most popular - unplugging the camera, re-installing the drivers, re-connecting the camera and re-opening VidGrid will fix the issue.
Download latest drivers here: https://support.logitech.com/en_us/product/hd-pro-webcam-c920/downloads