How can John Lewis wipe out three years of my extended guarantee?

The £100 extra was sold as ‘Added Care’ but when I came to claim, I couldn’tIn 2018 my mother purchased a £379 Bosch washing machine from John Lewis and, at the same time, paid an extra £100 to extend the guarantee to five years.The machine recently broke down, but John Lewis won’t fix it because it says it is outside the two-year guarantee. It seems that when she bought the machine, it failed to register the added care policy, which appears to be admini