More edge cases, more documentation. If we don’t push the small rocks up the molehills, how are we going to make mountains out of them?
For future reference – hello future, I hope you’re out there doing ok, I hope this helps – the symptoms of the problem are that the MacOS Accessory Security dialog that prompts you to allow a USB device to connect flashes on the screen and then disappears before you can interact with it, and new devices refuse to connect.
In the logs in Console.app, the line that appears will read “device functionality blocked by transport restrictions”. As far as I can tell there’s no documentation about this out there, and there’s no visible recourse in the UI.
Fortunately, the solution seems (seems…) to be straightforward. It look some plist file somewhere got corrupted somehow, so we just need to nudge the OS a bit to convince it to straighten up and fly right.
I’ve solved the problem by going into the Privacy And Security section of the MacOS settings, changing the preference from “ask every time” to the “allow accessories to connect when logged in” option, then changing it back.
It’s inelegant, and I am never happy when I have only made a problem go away instead of actually understanding and fixing it, but it seems to work. It Works On My Machine. It’s MacOS, you take the wins you can get.