Minecraft Launcher & Badrock on a company computer

I have a company computer with an Office365 subscription through the company. 
However, I am allowed to use the machine for gaming as well, so I have added a private Microsoft account. 
Unfortunately, the launcher for Win10 does not work because the Mincraft lancher does not ask which account to use. The lancher for Win7 works, but cannot launch the Badrock edition. 
I was able to install the current Badrock edition, and launch it without the lancher. However, the login to the Microsoft account fails here as well. 

Error code: 0x80040154 Code: Deep Ocean. Something went wrong in the login process.