If the TV has no video from all sources, please follow the below methods to do the troubleshooting:
1. Unplug all video sources from the TV and check whether you could enter the home page of the TV.
2. If the TV has internet access, please check if there is a new version of software updated online or not.
Press the Settings button on the TV remote, then select Settings-->System --> About -->System Update --> Network Update:
If the issue is not resolved, please feel free to call the TCL hotline for further help.
