Please check if the LED indicator blinks when pressing the Power or Reset button, if it doesn’t blink, then you should change the battery.
If it blinks, but still can’t turn on the computer, please try the following steps:
(1) Unplug the computer’s power cord, pull and insert the card several times and check if the expansion slot is dirty. Use an eraser to clean the gold fingers (connector’s metal pins), then re-insert the card.
(2) Check if the POWER SW and RESET SW are connected in the correct position, be sure they are not loose.
If these steps do not work, then check in motherboard’s BIOS/UEFI menu to make sure PCI-E functions have been enabled.