Roleplays that tend to die out quickly are a major pain. It's either one of these problems in my opinion:

A. The GM didn't plan out things properly and thus players are confused.

B. The players lose interest or fail to perform properly causing alienation to other players.

C. The characters don't fit the style of the roleplay and it collapses due to the player characters unable to do things together properly.

D. Real life rears it's head and slaps you with it's back hand making players take longer to post and thus losing the spark.