ASUS 660 TI cannot detect the card

hi! need help with my ASUS 660 TI OC installed in ASUS Z77 SABERTOOTH. at first it worked fine win inserted on the first slot, then later he board cannot detect the card.
Then i decided to transfer to the 2nd slot, same as above at first it worked fine the later it was not detected, same as when i transferred to the 3rd slot.

please help for i cannot i figure out what seems to be the problem