I just bought minecraf java edition and the launcher only lets me play demo and I already redeemed the code

Hello,

Unfortunately our teams are not able to help you with this technical problem which is not a problem with your code itself. You must contact Mojung support for help.
https://help.mojang.com
They are used to handling technical problems with their games and can solve your problem easily.

We remain available if needed.

Cordially.