Need more info. What did you do? What did u change? Could be any number of things. Did you put the strut back in the spring properly?is it the proper strut for the car? Looks too long
That's not an unoccupied hole there are only 2 bolts on that car the other one is directly across from the other one. I changed my rear struts yesterday and it's 2 boltsIt looks like you have a broken strut mount and possibly have a snapped bolt too judging from the unoccupied hole in the picture. Get it replaced.