Had to migrate to MS, so I did.
Re-downloaded Minecraft (because new computer)
Tried to login and got an error message: "Check your Account Minecraft Launcher is currently not available in your account." Error code: 0x803F8001.

Followed advise of communitymember and downloaded the original launcher, but was unable to login, since my mailadres of password are seemingly invalid (and I know for sure I used my microsoft account here ) nothing helped..

So I cannot use the new launcher and the old one does not accept my password.

SO HELP PLEASE!!!!!