Missing source | Quartus

I trying to make a make a system takes in a 3 bit line and flips put to a specific bit, like two's complement. I am struggling to reconstruct my bit bus after manipulating my bits. Specifically, it says My bit lines are missing sources. I am struggling to understand how it thinks a line coming from the input pin and a line going into my mux is two destinations. I am tried multiple ways of connecting the wires and all seem to fail for me. Can someone please explain to me the best way to concatenate my buses for a function like this.