Do you currently have any other Zigbee devices connected to your C-8 Hubitat Elevation hub?
If yes, are you using Homebridge on you Mac Mini to integrate these Hubitat devices with HomeKit? Or is Homebridge being used for other non-Hubitat-connected devices? The reason I ask is because Hubitat has built-in Apple HomeKit integration that you can use to add Hubitat-connected devices to Apple HomeKit directly, without needing Homebridge running on a separate system.
If you'd like to try Hibitat's built-in HomeKit integration, please take a look at the following Hubitat documentation.
