Whenever I open the Minecraft Launcher for Windows 10 it asks me which account I want to select. After that I click on my Microsoft account and it connects me to the launcher via XBox Service. After that I get the message every second that a connection to the Minecraft services is not possible, but shortly afterwards the message disappears, but reappears a second later. This happens all the time while I'm signed in with my Microsoft account. I can only play the demo versions and the game button switches between "play offline" and "play demo", even Java I can only play in the demo, although I've owned Minecraft Java for years. But as soon as I switch to my Mojang account in the new launcher, the constant connection errors disappear and it only shows me that I can play the demo and have to buy Minecraft. And when I go to Buy and sign in with my Microsoft account, nothing happens. When I go to the Minecraft website and log in it also tells me that I own Minecraft and when I go to buy it just says I can download it again, so obviously I own it.

It is the same issue that Aske Bisgaard Vammen had and i also turned off my firewall and it still didnt work.