Im trying to log in so I can download apps to my new iPhone, but when I try to log in i get a message saying that I need to look at the settings of my old phone. Is there a reason why I’m getting this message and what does it mean?

i got an iPhone 11 as a gift for my partner. She previously had the iPhone 6S Plus. So the issue I’m having is that she can’t sign in to her Apple ID on the 11. Instead she gets a message directing her to wait for a message from her old phone but she gets no message. Does anyone know what you’re supposed to do? I’m on hold with Apple and have been for the past 30 minutes, so any help would be great.