This one is almost unforgivable. When someone made the decision to make a movie out of '50 Shades of Grey,' all they had to do was pick a pair of lead actors who had intense, sizzling chemistry together. Turning this book into a movie was all about getting that chemistry right (because let's be honest - there's nothing else to the source material!). There should have been enough time to audition potential actors together and make sure they got a great pairing. According to Jamie Dornan - who landed the lead role as Christian Grey - they didn't manage that.
Although he didn't ascribe any blame directly to either himself or his co-star Dakota Johnson, Dornan says they didn't have any natural chemistry at all. He also said that shooting together with her was 'very uncomfortable.' There's no further detail available, but the general impression is that they just didn't get along. The producers had one job here, and they failed to do it.