When a Windows 10 (patched with latest updates) Computer Is suddenly powered off from sleep mode (Such as plug removed) the Logged in session is lost. This requires a re-login. This effect Microsoft Account Logins unknown about Mojang accounts. 

Expected Functionality: 

User session is saved similar to normal shut down

steps to repro:

1. login to launcher
2. Start Minecraft 
3. Close Minecraft (whether you start a game or just fully load the menu)
4. Go to Start > Power > Sleep
5. Hard shut down or remove power from computer
6. turn computer on
7. launch Minecraft launcher