Due to BIOS different, i5-4258u mini pc setting for “Restart Automatically after a Power Loss” is different than the last guide we issue in this link: http://support.hystou.com/2015/09/12/how-to-make-your-hystou-mini-pc-restart-automatically-after-a-power-loss/
If your BIOS is same like this pls follow guide here:
Click Chipset and go to PCH-IO Configuration
In this screen you can enable or disable wake on lan function, Restore AC Power Loss and others. Restore AC Power Loss is the one we are talking here, click to select the right one you want will be OK.