I've been lifting seriously for about five years. It's always been difficult for me to put on weight but I've managed to go from 180ish to a solid 210 in those five years. The problem is I hit 210 exactly a year ago today. Over the last year, despite no drop in my intensity and diet, I haven't gained a single pound and my lifts have remained pretty much the same.
I've always practiced muscle confusion in my training and maintained a constant bulk 6000+ calorie diet + supplementation. In fact I'd venture to say that the last two years have been my best years with the addition of a 5 day a week training partner.
I have no idea what could be holding me back. 210 is the biggest anyone in my family has been; my dad was 170 in his weight lifting days. Can genetics hold you back, or in my case, stop you dead? I'm 26yrs old, so these should be my best years. Needless to say, I'm pretty discouraged. A year without gains is pretty rough.