[TROUBLESHOOT] “Can’t find object” when trying to expand room or build wall

@NumeroLetter I am not experiencing that error on Bedlington Boathouse in my game.  I am, however, working with the build that came with the expansion pack.  Is it possible you placed a different build on that lot?  If so, there might be something problematic with the particular build you downloaded from the Gallery.  Try starting a new save and testing the original build that's on the lot.

I'm having the same problem on the same lot. I have no CC or mods, only a couple expansion packs, it is the house that came with the lot. I played with a different sim in the house before in the same game file and didn't try to change the house, then moved them out. There was a trash plant right outside of the lot grid but nothing left in the house or on the lot. I can't edit any walls

We had a fix for this go out in the EP07 Patch in June. If you're still seeing this error, could you upload the lot in question to the Gallery, or share a save file with me? Thanks for the help!

http://answers.ea.com/t5/The-Sims-4-Bug-Reports/INFORMATION-How-to-Send-User-Files-to-The-Sims-4-Team/m-p/6065302

Some umpteen years later, this problem popped up.  I'm trying to extend a basement on my lot.  It has no platforms and I was able to build the basement.  I've played other lots, returned to this one and this 'Can't find object' came about once again.  Can't extend the roof.  Basically, anything having to do with build are unable to work.

The lot is part of my base game in Glimmerbrook, Brooks Bridge Borough.  None of the other lots there are affected like this.

I exited the game, started it again, and went straight into Build mode for that house. I was able to extend the basement and any other build tool I wanted to use. Went back to Manage Worlds, and entered the house through the family.  That worked.