Put the summary of the bug you're having here

What I expected to happen was...:
I bougth the minecraft java edition for my son on minecraft.net using my microsoft user.

Afterwards I downloaded and installed the software.

Now, my son wants to play minecraft using his microsoft user on the same PC but after starting the minecraft launche only the demo version is available.

What actually happened was...:
see above

Steps to Reproduce:
see above

Do I have to cancel the purchase with my account and then purchase the software again using the account of my son? (when yes, how do I cancel the purchase?)

Or which other possibilities do I have?