Here are some tips if you're having trouble mirroring your phone:
1. If your phone or tablet will not display, it may need permission from the TV. Restart your device and TV, and then try connecting again. Make sure you select Allow when it displays on the TV.
2. On a Samsung TV, you can bypass allowing permission for your device to access your TV. From Settings, on your TV, navigate to General, and then External Device Manager. Navigate to Device Connect Manager, and then select Access Notification. Set this to Off to automatically connect with the device when using Smart View. From the Device Connect Manager screen, you can also select Device List to manage the devices connected to your TV.
3. If your screen keeps turning off, change the screen timeout settings. From Settings, search for and select Screen timeout. From there, adjust the settings so your phone or tablet stays on longer.
4. If the Smart View menu is minimized, tap the Smart View icon on your phone or tablet. The Smart View Control menu is only displayed on your connected device.
5. If the device's image looks small on your screen, you can make it a little bigger by changing the aspect ratio. On your phone or tablet, tap the Smart View icon, and then tap More options (the three vertical dots). Tap Settings, and then tap Phone aspect ratio.
From there you can choose your desired aspect ratio. Most TVs will look best with a 16:9 aspect ratio.