I restarted my modem and router yesterday — something I do every month or so — and I couldn’t get Siri to turn on my TV almost immediately after that. This hasn’t happened before. Since I could still view the PiCamera and control my Air Purifier, I assume it was a problem with the Harmony portion of Homebridge. A quick status check displayed the following errors…

Dec 17 07:39:16 HomePi homebridge[12398]:   errno: 'EHOSTUNREACH',
Dec 17 07:39:16 HomePi homebridge[12398]:   syscall: 'connect',
Dec 17 07:39:16 HomePi homebridge[12398]:   address: '192.168.1.16',
Dec 17 07:39:16 HomePi homebridge[12398]:   port: 5222 }
Dec 17 07:39:43 HomePi homebridge[12398]: Unhandled rejection TimeoutError: operation timed out
Dec 17 07:39:43 HomePi homebridge[12398]: at afterTimeout (/usr/local/lib/node_modules/homebridge-harmonyhu
Dec 17 07:39:43 HomePi homebridge[12398]: at Timeout.timeoutTimeout [as _onTimeout] (/usr/local/lib/node_mo
Dec 17 07:39:43 HomePi homebridge[12398]: at ontimeout (timers.js:475:11)
Dec 17 07:39:43 HomePi homebridge[12398]: at tryOnTimeout (timers.js:310:5)
Dec 17 07:39:43 HomePi homebridge[12398]: at Timer.listOnTimeout (timers.js:270:5)

A quick sudo systemctl restart homebridge fixed the problem.