Tom has the same concern I do: maybe this isn't an analog Polycom. Which is the reason I suggested using your test set.
His point about dumming down one of the first ETR ports would work well, too. I assumed the Polycom and Partner phone were to work together "more intimately." :O)
And yes, you need two pairs to get the Partner to work correctly. I use the 568B standard, which translates to the blue and green pair. A better description is the centermost pair, and the pair flanking (just outside) the center pair.
The AUX port on a Partner phone is essentially a bridge of the blue / talk pair, which is where my second suggest came from.