O3 wont turn off low power state after arming.1. My betaflight osd is there, so the rx tx connection should be good.

2. Uart msp connection is correct because I only have 2 uart, uart 1 for crossfire and uart 2 for o3.
3. I have flash fc, downgrade o3, change tx rx wire.

Anyone happen to have same issue? or maybe already solve the issue?

Your unit power off when arming?
For me too (perhaps with new Mamba H7 MK4 v2): in this case the problem is BEC on FC, that don't erogate the current (minimun BEC 9V @ 3A). I use an external BEC for positive and negative (unpin from connector) and work perfectly.

I have the same problem, I have betaflight osd on my glasses but I can't get out of low power after the poor thing.
I also noticed that I can't see the drone's battery voltage in the DJI OSD (0.00v)