There are some settings within Safari that will prevent Vizy's video window from displaying live video.

Go to Preferences➜Websites➜Auto-Play and make sure that Stop Media with Sound is set When visiting other websites. This is the default setting. Alternatively, you can set this for vizy.local. (A setting of Never Auto-Play will result in the Vizy's video not playing.)

If you're using an older version of Safari (older than 15.5), you may need to enable the Develop menu and select Develop➜Disable ICE Candidate Restrictions from Develop➜WebRTC to see video images from Vizy: