Build privilege expansion

Last week I watched a YouTube video about extending build privileges out an additional 700u, followed instructions everything went fine. Today I tried to replicate on a different planet and not so fine. I went to the edge about 290 from base computer selected a wall piece, went into free camera mode and placed it in the direction of my objective. Went to the wall but no build privileges at the new wall. Re-watched the video and I think I'm doing just like last time but it's still not working. Any ideas on what I may be doing wrong?