Try these troubleshooting steps if you are seeing a blank/black screen:
Try connecting Nex Playground to other HDMI ports on your television.
Try disconnecting all other connections to your television. In some cases streaming devices or receivers may interfere with Nex Playground connection.
Try another HDMI cable, if possible.
For Samsung TV customers, try using the HDMI Troubleshooting feature:
Press the Home button on your remote control and navigate to Settings > Support.
Select Device Care.
Select Self Diagnosis.
Select HDMI Troubleshooting from the menu.
Check the connected HDMI ports in sequential order.
If the issue persists, please reboot Playground by unplugging and plugging in with the original power cable.