Android File Transfer "Could not connect to the device"

The Android File Transfer app for macOS keeps telling me "Could not connect to the device. Try reconnecting or restarting your device" but reconnecting or restarting won't make a difference. By chance, I had to create a new user account on my computer and my phone was still plugged in. I was surprised that the File Transfer tool launched straight away and worked without flaw!

I have since tested it several times. My user account won't work, new user account works. This makes me believe its a cache, settings, preferences related problem but as far as I can see the app only creates 1 file which is a plist that tracks which folders you had open. I deleted this file but no change.

Does anyone have any suggestions what file/setting inside my user profile might be causing the connection to fail?