Problem:

Source change is not possible after setup

Solution 1:

Update the software to version 1147.1 or later (online), or cold boot the TV.

Cold boot methods:

Unplug AC power cord or press and hold Power button on remote.

Solution 2 :

Re-setup the TV and choose either "I do not receive a TV signal" or "Antenna" in Select Your TV Source. Update software to 1147.1 or higher even if issue is fixed.