Making a block diagram and I get the error "missing source signal"

I'm using Quartus Prime Lite Edition. The error I'm receiving is;

Error (275044): Port "datab[3..0]" of type multiplier of instance "inst" is missing source signal

I've checked my block diagram over and over and all of the connections are there. Can anyone point me in the right direction? Please see attached image.

Cheers.

Attached Images

• source.PNG (16.1 KB)