PL is obviously taking the path of least resistance in "attempting" to provide a resolution. The Powerful Partnership of PL and UA seem to be weak in correcting a wrong they perpetrated. If, theoretically, UA were only able to deal with the airfare portion, which PL has already rectified, then the onus would be on PL to handle the hotel portion. Obviously, they are disinclined to do so, either through incompetence, sloth, greed or inexperience. I wouldn't expect a chargeback to fail.