Search Complete, Still Can't get Rear Derailleur Working

I'm guessing it still may not be tight enough (the cable).

As I recall, I like to put the shifter in the position it would be in to be in if you wanted to be in the small ring.  Then, you have to push the derailer by hand to the second or third ring up from small one (the springs want to pull it back to the little gear), THEN tighten down the cable.  When you let go, the springs will pull the cable to it's max. limit and derailer should fall back to the small ring (or close to it).  If it doesn't slowy release the cable and let the derailer slip to the right gear and tighten.

Most likely you will have to make some small adjustments with the barrels, so it's best to have them in the "middle" when you start, so you can loosen or tighten them if needed.

I could be wrong, so you might want to wait for other wrenchers to chime in.

Is it possible that you attached the shifters while they were set to the lowest gear (biggest cog)?  The default position of the derailleur is of course on the smallest cog.  The cable should be taut.  You can test the shifting of the derailleur by pulling on the cable directly and in so doing the shifting should occur.  If you can do that, the derailleur is probably fine, and it is a problem in the shifters.  If you can't shift it "manually" this way, it might be that for whatever reason the limit setting screws are off.

If you have mis-set it, first loosen the bolt holding the cable in place on the derailleur, then shift to the highest setting on the shifters and re-tighten the bolt.  It should now work fine, possibly needing some adjusting with the barrel for fine tuning.  Good luck.