Don't know the TV but has the TV got any button controls on it, such as Power On/Off, Vol Up/Dn, Menu, Input etc?
If so try removing the batteries from the remote control unit and check if you can turn on the TV OK when using the TV controls and not the remote.
If this works OK test the remote control using a digital camera or the camera in a mobile phone to make sure that it is working OK.
Turn on the camera or start the camera app in the phone and then point the end of the TV remote that is normally pointed towards the TV, towards the camera lens so that you see it in the camera’s or phone’s LCD screen.
Press a button on the remote and you should see a light flashing at the end of the remote when looking at it in the LCD screen.
Try pressing the Power button on the remote and make sure that the light goes on and off when the button is pressed and released.
Make sure that there is no light showing when NO button is being pressed.