I finally got AA to work on my X8. Turns out, the USB Configuration default was "Charging only". Plugging into the car USB port didn't trigger a prompt to change configuration. The prompt popped up when I plugged it in while playing media over Bluetooth. I changed default to "File transfer / Android Auto" and now it has been working for the 5th straight day. A slightly different behaviour from my previous Pixel and Sony devices is that the phone needs to be unlocked with the cable plugged in the cable for AA to be activated.
For those who has similar problem, hope this info helps