This happened to me two days ago with my '17 Starlink head unit.
Left phone connected via USB and briefly shut off car to run inside. 2 minutes later, I start the car and the
HU wouldn't turn on. Tried cycling the power a few times w/o my phone plugged in, but still no power to the HU.
Feeling defeated, I drove to my destination exclusively listening to the Corsa exhaust instead of my OEM Audio Plus system
. Had to reverse park without my backup camera which was a throwback to my FR-S days -- I rely too much on the camera these days.
Let the car sit for 30+ minutes and when I went to start the car,
the HU turned on again with no loss of settings.
This has happened one other time in the past and I wrote it off as a fluke / glitch.
I wonder if the phone connected via USB is draining a capacitor in the HU causing it to not turn on? 