One of my two apollo batch 1 after being shut down, it didn't work anymore. When turning it on, only the fan runs for 1-2 s and stops. The front led has no activity and the network card leds appear to have normal activity. I already cleaned it and tried to find any signs of damage but I can't find any.
What else can I try?
That front led is software controlled. It showing no activity suggests that the system doesn't boot at all or not correctly at least. In that situations your options are somewhat limited:
Option 1) Re-flash the sd card. In many cases that appears to help.
Option 2) Flash another sd card. The current one may be dead.
Option 3) The non-trivial option: Get a USB to TTL adapter and attach it to the uart of the mcu board. That will allow you to see what is happening during system boot and possibly give a clue what's wrong.