Recently you have to migrate your Mojang account to a Microsoft account.
Now I got this message in the Minecraft launcher:
"We have not started migrating to Microsoft accounts yet. We'll let you know when your account can be migrated. https://help.minecraft.net/hc/en-us/articles/360050865492-JAVA-Account-Migration-FAQ"
Now the FAQ page says that I should click on the announcement, but unfortunately that doesn't work.
What shall I do now?
I think they haven't started yet and just want to inform in advance.
The migration will not begin until January 2021 and everyone will receive an email with instructions.
Be patient.