If "Fast Startup" is enabled on Windows 10 or Windows 11 VDA on a physical machine, the published desktop might fail to start and display a gray screen.

Follow the steps below to disable fast startup on the VDA.

The fast startup settings in Control Panel:

1. Open the Control Panel, and click on the [Hardware and Sound] icon.
2. Click on the [Power Options] icon.
3. Click on the [Choose what the power buttons do] link on the left side.
4. Click on the [Change settings that are currently unavailable] link at the top.
5. Check the status of the [Turn on fast startup] setting.
6. Uncheck [Turn on fast startup], and click on [Save changes].

Distinguishing Fast Startup from Wake-from-Hibernation
https://learn.microsoft.com/en-us/windows-hardware/drivers/kernel/distinguishing-fast-startup-from-wake-from-hibernation

Problem Cause

When fast startup is enabled, the VDA machine is hibernated instead of being completely shut down.
Although this is an internal operation that is different from normal OS shutdown/startup, this behavior is not expected in the Citrix Virtual Apps and Desktops environment and may cause a session launch issue.

Troubleshoot Gray or Black Screen