The VirtualBox error “VM Session was closed before any attempt to power it on” usually occurs when the user shuts down the host machine without shutting down the VM guest machine first.
How to FIX it ?
Method 1. Discard VM’s Saved State
To do that:
1. Right click on the Virtual Machine and select Discard Saved State
2. Then try to start the virtual machine. If the problem persists, continue to the next method below.
Method 2. Uninstall and Re-Install VirtualBox
The next method to solve the “VM session session was closed before any attempt to power it on” problem in VirtualBox, is to uninstall and then to reinstall the VirtualBox application, especially if the problem appeared after a Windows Update.
1. Go to Control Panel & Uninstall VirtualBox. (Don’t worry, the VMs will stay untouched).
2. Reboot your computer.
3. Download latest version of VirtualBox.
4. Right click on the downloaded file and click “Run As Administrator”.
5. Follow the on screen prompts to install VirtualBox.
6. After installation, reboot your computer.
7. Open VirtualBox manager and start your Virtual Machine.
8. If the Virtual Machine opens fine, then proceed to install the Guest Additions and the Extension Pack (if needed).
