The Philadelphia Union's USL side is unable to play in the United States Open Cup per new rules.
In a move that makes sense (but probably could have been handled better), Bethlehem Steel FC are one of eight USL clubs that cannot compete in the US Open Cup moving forward. The rule is that if a MLS side owns a USL or NASL club, that club can no longer compete in the US Open Cup. Maybe it's to avoid potential conflict of interests between parent club and affiliate, maybe it's so there's not 16 USL clubs in the quarterfinals.