Had a similar issue....for me, it was wanting support. Without pillars available to me, I just made some arches with door frames for now. Then I could place the pieces I needed.
#Cant place build plan
mint gull
cunning berry
It may need more structural support, I'd try placing some support beams and see if that helps
warped sinew
hmmm it wont let me place anything up there at all no suppor beams walls or doorframes
woncder if if my house is to big
cunning berry
How many floors do you have?
cunning berry
Hmm maybe there's a build height? I'm not sure
warped sinew
okay so think i figured it out
walls need to have a direct line to foundations or you cant place them the same with door frames and you cant place the roof more than one space in each direction of a wall so will need to put up walls on each of my foundations to fix it
warped sinew
well i havent unlocked that
cunning berry
I got mine from a puzzle reward in a beginner area!