Traiden Killer trapdoor. It doesn't work for me. Please help.n

I'm in the beta program and the Triaden Killer trapdoor for killing mobs hasn't been fixed for me. It worked for me before, but in this latest update, 1.21.100, I tried to leave the beta and it won't let me load the world. Why? It tells me the world was created in a current one. I wish I could continue in the beta, but what? Can you give me a solution to the Traiden Killer? Thank you very much.