Can I spawn the Wall Of Flesh twice? I have spawned it once and I don't want to try and get another voodoo doll and not be able to use it.
Yes, you can spawn the Wall of Flesh twice. In fact, you can spawn it multiple times.
I think I know your problem. After you spawn the Wall of Flesh, your Guide will be killed.
After you defeat the Wall of Flesh, you CANNOT fight it again immediately.
You have to wait for the Guide to come back before you kill it again to spawn the Wall of Flesh.
Take note that you need the Voodoo Doll of the Guide and throw it in lava, then you can spawn the Wall of Flesh.