Samsung Galaxy S10 Mirror Screen

My wife and I both have Samsung Galaxy S10 phones. We recently got a Samsung TV (RU7100). I set my phone up with the TV and I have all the functionality working. I added my wife and her phone can do everything except for mirroring her phone screen. She can control the TV, use screencast from some apps (like YouTube), and play the TV sound from her phone. Does anyone have any suggestions about what may be wrong?