When you have this issue, please try:
1: Shut down, check whether the power level is correct, if not, set it to the correct position and then power it on again.
2: Open the cover, check whether the internal motherboard and power indicator lights are on.
3: If the power supply does not respond, check whether the switch fuse is damaged. If it is damaged, replace the fuse.
4: If the power supply lights up normally. Check whether the motherboard port has 24V input. If yes, probably the motherboard issue and replace the motherboard. If not, replace the power supply.
5: The motherboard indicator light lights up. Please use putty to flash the firmware.