When exploring my new master world and coming across the dungeon. I accidentally broke a few bricks from the entrance of the dungeon floor. I placed them back and didn't think much of it. After defeating golem and waiting for a few days, I noticed the cultists nor the tablet still didn't spawn.
After investigating for a bit, I realised the bricks I broke caused it, and even placing them back doesn't help. If you know why this happens and how to fix it, I will be more than happy for you to tell me.