In the Windows OS, right click , and select Device Manager. Then you can check whether the Magewell unit is in the Camera list.

Not found: Check whether you have used the cable provided by Magewell, or you can connect to another USB port.

Found: Check the privacy settings. Please refer to  the 3rd section in Can't use or find Magewell capture device on Windows.

In the macOS,  click Apple icon > About This Mac > System Report.  Then you can check whether the Magewell unit is in the Camera  list.

Not found: 1. Check whether you have used the cable provided by Magewell. 2. Connect to another USB port. 3. If you have changed the color space with  USB Capture Utility V3, refer to Video capture software can't find video capture device after changing the color format in USB Capture Utility V3 (Mac).

Found: Check the privacy settings. Please refer to the 3rd section in Can't use or find Magewell capture device on MacOS.