the room on the right(the one the player is in) says its ‘missing a wall’ the lower right one, with the furry NPC is fine? What wall am I missing?

Check the sloped blocks, they hide behind them sometimes. Otherwise just auto place the walls around until it solves the problem.

The platform that is a stair counts as a diagonal block connection, which means that the room isn’t fully enclosed, but another platform right below the stair and it should be good