A black screen when connecting to a Horizon virtual desktop can be caused by various reasons, such as network issues, hardware issues, Horizon tunnel issues, or underlying guest operating system issues. Based on the options given, the following could be the cause of the issue:
A vRAM shortage on the Horizon virtual machine. This can affect the display performance and cause a black screen or a disconnect. To resolve this issue, you should configure the pool to provide enough video memory for the resolutions you plan to present to the clients1.
The incorrect video driver version installed on the Horizon virtual machine. This can cause compatibility issues and prevent the display protocol from working properly. To resolve this issue, you should verify that the View desktop is using the correct video driver and that it is compatible with the VMware Tools and Horizon Agent versions installed23.
An incorrect firewall configuration. This can block or misroute the display protocol traffic and cause a connection failure. To resolve this issue, you should verify that the required ports are open between the client, UAG/Security server/Connection server, and VDI machine4 .
The other options are not likely to cause a black screen when connecting to a Horizon virtual desktop:
The client machine video memory is too high. This should not affect the display protocol performance or cause a black screen. The client machine video memory is only used to render the display on the local device, not on the remote desktop.
The Horizon virtual machine video memory is too high. This should not cause a black screen or a disconnect either. The Horizon virtual machine video memory is used to allocate resources for the display protocol on the server side, not on the client side.
References:
Dual monitors configured using PCoIP does not span both the monitors for VMware View and Connecting to a VDI desktop with PCoIP displays a black screen and disconnects after 10 seconds
Error attaching to SVGADevTap, error 4000: EscapeFailed reported by PCoIP server
Interoperability Matrices
Configuring PCoIP Secure Gateway in VMware View
[Network Ports in VMware Horizon]
