Excuse me if this has already been discussed, but if not....

You need to change the Scoring and Settings from "Playoffs: None" to "Playoffs: 3 Rounds." If you don't, there will be no playoffs.

It's an error by Yahoo that's going to have a ton of angry people in about 3 weeks. If you choose "same settings as last year" in the beginning of the season, for some reason Yahoo defaults to no playoffs.