u/Confesto

I know the title isn't catchy, but really. On Java Edition, Asus tuf gaming f16 if you need the facts, I have a superflat world in 26.1.2 , it is very big and great, but when I do "/place structure minecraft:mansion" it just says "Failed to place structure", even if I am on higher ground, can I get help on how to place it, why soem structures can not be placed, and why and its gimmicks? I am a player, not mush of a thinker and I cannot find videos to help on youtube or posts that help on reddit.