Why didn't my brioche rise? This weekend I attempted to make this recipe for brioche.  I did the first step and combined the the milk, yeast, 1 egg and 1 cup of flour which caused very big clumps and then I added the sugar.

I then did the 2nd through the 5th steps but the clumps stayed and the dough was really wet (like pancake batter) so I tried adding more flour until I got something like the right consistency. I then covered the dough and put it in a draft free area that was warm for 2.5 hours but my yeast did not rise and the dough still had clumps in it. I waited longer but nothing so I had to throw it away.

I really wanted to try this recipe again so I would appreciate any insight into what I did wrong.
First, try proofing your yeast (mix 110°F water, a little sugar, and a little yeast in a small container; confirm that it foams). It may be that your yeast is (well) past its prime. That's the most likely reason I can think of that your dough didn't rise.

Second reason could be that while mixing, the dough got too hot—heat will kill yeast. Yeast dies somewhere around 130°F, but really you want to keep it much cooler than that. If its getting too hot, consider starting with colder ingredients (e.g., ignore the instruction to warm the milk).

Finally, I'd suggest using recipes that are by weight; flour is much easier to measure by weight. You may be using a different scooping technique than the recipe author.

Also—there is something weird about that recipe. It lists 3½ cups flour in the ingredients, but then only has you add 2½ cups in the steps. I suspect that is a mistake, and explains the batter-like consistency you got.