xbox live gold card

my son received a 12 month subscription card for christmas he entered it on 1-18-2019 and on 2-3-19 it went out and cant play fortnight. it says on his xbox when he entered the code but i cant get anyone to help on any sight i been on i cant continue tp
buy gold cards if this happen. i still have the card from this last time and re-entered it and it says this has already been redeemed but says we need a new one on his xbox

:)