It is possible the f/w you have is not for that TV. BUT normally it is checked and the update rejected if it is wrong.
It is possible the board you have is not exactly the correct one. All numbers must match the old one.
It might be possible there is a wrong connection. Try as I may, I sometimes do that.
It may be possible the "new" board isn't totally functional. That happened to me once or twice.
It may be possible there is another problem.