In order to turn on the mini PC automatically when the power is connected, you need to activate the feature in BIOS settings.

• connect a monitor with HDMI and a USB keyboard to the mini PC and turn it on.
• when the system is on, before the OS boots, you need to keep pressing F2 button to enter the BIOS. Then:
  1. Go to “Power” tab.
  2. Click on “Secondary Power Settings”.
  3. Scroll down to “After Power Failure” and choose “Power On” from the dropdown list.
  4. Save and exit.