do you understand what the various components do in your circuit? look at each one's datasheet. pay attention to the inputs and outputs. ISIS must have a way to look at the inputs and outputs of the chips. so, when you push a button, the 373's outputs will change. the top switch (input to d0) should cause the 373 to output a low on Q0. look to see if that happened. if not, there is your problem. if it's ok, look to the next chip, the 147. see if the outputs make sense given the inputs. if the low on input 1 causes the 4 outputs to be L, H, H, H (q0 - q3) then it's good. then follow the inverters ('04) and finally, check the 47.
by the way, original schematic used proper pull-ups.
another point, your isis diagram is kind of a mess, it's very hard to tell whether 2 lines are connected when they cross.