Eternaland Building?? How do I do it?

I logged on today and my blueprints and stuff were gone so I figured the game scenario thingy or whatever was over so I googled what to do. It said go to eternaland so I did and Mitsuko told me to break berries and then to "build the house". What house? There is one huge house in the background that's already built and I can't build any of my saved blueprints or the default saved blueprints. Whenever I try to place anything it says building formula locked. I have thousands of the sand stuff but I can't build anything. I don't care about my blueprints and all the stuff I lost cause I like resetting and having to get new stuff and make new characters all the time it's fun! I want to continue doing the eternaland quests but can't if I cannot "build the house". Help? (I've been googling for the past hour and looking on Reddit for what to do but no helpful answers)