Some Note 9 users report their navigation keys (like the Recent and Back buttons) have stopped working.
Please do not attempt to have your device replaced or perform any data wipes for this behavior. This is due to a recent update to Samsung Pay Application (version 3.0.0) and a permanent fix is expected to be available soon. This behavior may be seen whether Samsung Pay has been set up or not.
A temporary resolution is to swipe away the Samsung Pay hint overlay three times, then disable the favorites card option within Samsung Pay to bring back functionality.
Dismiss the Samsung Pay hint overlay by swiping the image up three times.
Open Samsung Pay
Touch More Options > Settings
Touch Use Favorite Cards
Toggle each of the three sliders to turn off the Lock
*Note: This will prevent users from being able to swipe up from the bottom of the screen to open their favorite card.