I am so sick of #macOS and it's inability to consistently manage any sort of peripheral.
Normally I just bitch that it can't remember anything about my monitor setup. Now it will only communicate with USB or Thunderbolt peripherals if they're connected and powered on when the Mac starts up. Turn them on after that? Nope, Mac won't talk to it. Connect them after the Mac starts up (maybe connecting a flash drive or connecting to an iOS device? Nope, Mac won't talk to it.
#Apple. Honestly.