I'm knee deep in door hel...errr...fun and have, hopefully, a dumb question. Tonight as I attempted to install my strut, there is no way I can get this thing to compress. I did notice that I ordered a 625N vs the 600N that I intended to purchase, but that's a difference of 5 lbs... So is there a secret that I'm missing? I had almost my entire body weight (175) on the thing (hope the neighbors weren't looking) and it didn't budge. What am I missing..?