I have redeemed my old Warcraft 3 RoC CD-key and as laid out on the website (https://us.battle.net/support/en/article/23374) I should be able to acces The Frozen Throne as well, however that is not the case - The Frozen Throne installer from the website (https://us.battle.net/support/en/article/000194130) does not work for me (the CD key worked for RoC but not for TFT). I have also finished RoC campaign, but that did not unlocked TFT content as suggested in other threads. Could you clarify that for me please?
I have the original CDs of both ROC and Frozen Throne and each game has its own key. You would need to redeem the Frozen Throne key too and use it to install that game.