After the computer is disconnected from power supply (by unplugging the power cord) and re-connecting again to power supply, WOL function can NOT work and also standby status has disappeared. How can this problem be solved?
This is Normal, as because it is impossible to wake on LAN if the power cord is un-plugged from the system (even just for 1 sec). In order for wake on LAN to function properly, the 5V standby voltage from Power Supply is needed for LAN chip to store MAC address of other systems for sending/recieving signal. If the power cord is disconnected, 5V standby voltage supplied from the Power supply to the LAN chip will be lost and as a result, LAN chip will lose the ability to store MAC address and therefore cannot send/recieve signals from other systems.