What am I doing wrong?

B42 and I need cant just continuously build this wall, I have to reopen build menu and reselect the wall, I dont recall having to do this before.

https://preview.redd.it/38g0gfa2cpyf1.png?width=1621&format=png&auto=webp&s=7b5870fb6e2430f226b8d03578ac38ee11801905