US won't touch a ticket issued by an opaque third-party vendor such as Priceline. The agents can't even see what you paid and what restrictions, if any, there may be (not that this should matter for the below MCT connection).

A piece of advice is not to call US. It completely gums up the system and it is entirely possible that this reset the timing.

I would give Priceline two full business days and then call back. If not resolved, make sure that you have the specific flights you want in mind. Don't leave it to PL because they can gum it up worse.

When all is resolved with PL, give it overnight and then check your e-tickets on each operating carrier to make sure that what PL says it has done has actually been done.

Rinse, wash, repeat. You may find it frustrating, but the business model is based on volume & price, not customer service.