LattePanda V1 Auto Power On and RTC battery issue

Hi team,

I have LattePanda V1 4GB RAM/64GB eMMC, S70CR200-CC55F-212700760.

I have connected RTC battery, have enabled Power On feature in BIOS.

The first time LattePanda works normally. But after about 2 weeks, when I connect PC to power it didn't start. I tried a lot of time to disconnect-connect to power and it didn't start, and the red LED indicator not light up on the underside of the board.

Then I push power button and this board still isn't start.

Can you guide me how to fix with this problem?

Thank you so much!