My friend can't use Minecraft and I don't know how to help

Sorry for being vague, but my friend bought Minecraft back in 2021 and had a great time with the game, but his computer broke and and after buying a new one, he signed into minecraft.net with the same account and he downloaded the launcher, but all it says is to either play the demo or buy the game. Just so you know, he fully bought it and he played with the account. It was only when he got a new computer did it not work.