WC3 Reign of Chaos Key not recognised

Key not recognised. Tried installing WC3 RC key isnt recognised by the game even when i am getting the key from battlenet.
What is going on?

If you have an actual RoC key, you need to enter it in your battle.net account on the wbesite. If you’ve done that , it will show up here under “classic game accounts”
https://account.battle.net/games#classic-game-accounts

If you see this, then you will be able to install the game from the battle.net app. Sometimes the app doesn’t recognize this and to work around that, you have to click the gear login at the battle.net app login prompt and select “Continue without logging in” and then you’ll be able to install the game. Log back in normally and you’ll be able to play.

If you’re talking about installing an old version of the game, and the key isn’t being recognized, that means you either made a typo / otherwise entered it wrong, or you have a bad key. If this is the case, where did you originally get the key? If you entered it from an original CD jewel case, I’d check that- I’m not sure that the key show on your current battle.net is actually the same CD key. But I don’t really know there because it’s been years since I ever had to do that.