I bought Minecraft but can't play it?

I bought Minecraft today on Instant Gaming. (The site is not a scam, I've already bought a lot) Got the code. Created an account with Minecraft, redeemed the code and downloaded the Minecraft launcher. I can now start "Latest full version" in the launcher. However, only a time-limited demo version will start.

Does anyone know what I can do now?

(I have already reinstalled the launcher and of course restarted my PC. Doesn't help)

See if you can also enter the code in the launcher

So with a colleague I had the same problem and with him it was because it was not his Mojang account on which he had redeemed the Java version, but his Microsoft account.

He had to log into Java Minecraft with the Microsoft account.

Or the other way around

No, I described how it was with him ^^

Yes, I probably know. Did the questioner do it the other way around?

Thanks works now