Why is debugger saying shutdown occurred?

I’ve never had a problem, now starting this up (virtualbox) and choosing debug mode for windows, it connects like normal but then disconnect right away. What causes that? How do I diagnose issue? TIA!!

Here’s what happens:

Microsoft (R) Windows Debugger Version 6.12.0002.633 X86
Copyright (c) Microsoft Corporation. All rights reserved.

Opened \.\pipe\debugpipe
Waiting to reconnect…
BD: Boot Debugger Initialized
Connected to Windows Boot Debugger 7601 x64 target at (Sat Jan 6 15:36:30.964 2018 (UTC - 8:00)), ptr64 TRUE
Kernel Debugger connection established.
Symbol search path is: srv*c:\symbols*http://msdl.microsoft.com/download/symbols
Executable search path is:
Windows Boot Debugger Kernel Version 7601 UP Free x64
Machine Name:
Primary image base = 0x00000000002fc000 Loaded module list = 0x00000000003ae9e0
System Uptime: not available
Shutdown occurred at (Sat Jan 6 15:36:33.627 2018 (UTC - 8:00))…unloading all symbol tables.
Waiting to reconnect…

I did debug / kernel connection / resync and now it’s working.

that was strange.