If your guest is joining an Interview in Chrome, and sees a message saying "Unable To Start The Call", then there are few things you can check to fix it.
Enable "Hardware Acceleration in Chrome Settings"
An issue in the latest version of Chrome will cause this problem if a Chrome setting called Use hardware acceleration when available is turned off.
To check this, follow these steps:
Go to Chrome's Settings screen
In the search box, search for hardware
Make sure the Use hardware acceleration when available setting is turned to on
Make Sure You Have a Working Camera Selected
If the above steps do not help, this message can also be caused by Chrome not being able to receive video from the currently selected camera.
Specifically, if you have a virtual camera selected, make sure it's working properly, and troubleshoot by selecting your built-in camera instead.