@emmag4611: You can change your theme by swiping up from your Home screen and tapping on Settings > Themes, and choosing from the available options here (Wi-Fi or Mobile Data connection required).
For clarity, have you run Diagnostics via the Samsung Members app for the Vibration feature? If so, did the phone fail to vibrate during the 'Call vibration' and 'Notification vibration' test?
As a basic troubleshooting step, please try pressing the Volume Down and Power buttons together for around 10 seconds until the phone restarts, as this will refresh the software and address any temporary performance issues. Don't worry, this won't affect your personal data or settings. Following the reset, head to Settings > Sounds and vibration > Sound mode > Sound > Vibrate while ringing > On > Call vibration pattern (make sure that 'Silent' is not select) > Back > Notification vibration pattern (make sure that 'Silent' is not selected).
Let me know how you get on.