Yeah jimmy, the Miller-Urey experiment is the go-to icon for OOL, and it turned out to be flawed. It took them 30 or so years to realize that they had not simulated the Earth’s primordial atmosphere properly.
Why it took them that long, who knows. Maybe they didn’t look at what the primordial atmosphere was like until the 1980s. Maybe they knew before then, but didn’t bother revising the OOL experiment for some reason. Meh.
Here’s a source about the non-viability of the “primordial soup” theory, of which the Miller-Urey experiment is the linchpin:
http://www.npr.org/templates/story/story.php?storyId=123447937
That experiment was over 60 years ago and since then similar, related experiments based on different assumptions regarding the early Earth have produce similar results, and many other organic chemical precursors of life.
Of course it's all still hypothesis, not theory or fact, but some of it very interesting.