This issue occurs because your TV does not support the higher resolution.
Switch off the power for your box and make sure that the adapter’s power light is off.
Switch on the power for your box and make sure that the adapter’s power light is on.
Press the standby button repeatedly after switch on the power.
The Startup Options screen will appear on your TV.
Press ‘987’ to access the Advanced Startup Options menu.
Then, press '1' to initiate a reset setting.
Press "OK" to confirm restore to factory setting.
After the factory setting is restored, TV will turn blank.
Please wait until the box completes initiate setup.
Press "1" to initiate Linux download on the software.
Once completed, the following screen will appear on your TV.
Refer to Installation Setup guide here to complete the setup.