I migrated my account and it seems like the process was not completed successfully. Trying to log in using my Mojang account tells me that the account is migrated and the Microsoft account tells me that I don't own the game!
I tried using 2 other launchers but the problem doesn't seem to be the launcher. It's most probably the backend of the servers being messed up.
Same problem here!
Logging in using Mojang: The account is migrated.
Logging in using Microsoft: You don't own the game!