iMac camera not showing up

We tried Jitsi for our family chat the first time this afternoon. Absolutely LOVED. My uncle couldn’t get his camera to appear in Safari. Is this a known issue? Huge thank you for all your hard work on this.

iMac (Retina 5K, 27-inch, 2019)

Processor 3.6 GHz Intel Core i9

Memory 32 GB 2667 MHz DDR4

Graphics Radeon Pro 580X 8 GB

Serial Number C02ZD02HJV40