An old-school diner sandwich, a French dip is really only as good as the bread it’s made with— which should be a baguette or a narrow French loaf that is decidedly crunchy, not soft and gummy. If the baguette is soft, put it in a 300°F oven for perhaps 10 minutes to get it crisp. That way, it’ll stand up to the “dip” (the pan juices) without becoming soggy.
There’s a slight chance the cooked beef might still be pink inside, depending on the thickness and density of the frozen shaved beef. If the meat is pink, turn the pot to HIGH on its SAUTÉ function after cooking under pressure and breaking up the beef. Cook, stirring often, until the meat is cooked through, about 2 minutes.