Wall of Flesh not spawning

I spawned the Wall of Flesh 3 times in my main world when I was trying to defeat it, as I knew this last time Iwas going to kill it, I tried to another (the fourth) guide voodoo doll into the lava and The Wall of Flesh didn't spawn, why is that?

Was the guide alive?

Oh, nope, that must've been the problem.

Eyeeup.
It was.
WoF can only spawn when the guide has moved in.