Consider resetting the TV to its factory settings if none of the other solutions worked. You can find the reset option in TV's settings.
Note: If you are not sure where to find the reset button, consult the TV's manual.
Maybe a hardware-related defect is the reason why you can't change TV channels. If you have tried all the other solutions, including a factory reset, but nothing changed, take the TV to a repair shop.
If your TV had a hardware defect and the hardware defect was severe and irrepairable, consider buying a new TV.
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