I'd be calling Marriott on both the PP and the Gift Card. I'm reading the back of a PP right now, and there is nothing there about blackouts. In fact, on a night when the hotel is sold out because of high demand (as that Louisville one was) is exactly when I'd expect to use a PP. That's a stay where the common promotional/non-public codes aren't available - everybody there is paying rack or close to it.

The PP battle may be subject to Marriott's interpretation of the last rule on the certificate: "Participating hotels may change." That rule is in conflict with the use of the word "any" on the front of the certificate in front of the listed brands that participate (depending on whether you have a 50 or a 100). But the Gift Card is unambiguous: there will be a Kentucky law that covers that one way or the other.