MTU Discovery is today not active as a default, you need to activate it on the VDA with a RegistryKey, the VDA must be at minimum 19.12, details here: ... - is the Registrykey set on the VDA - do you have Citrix Workspace App for Windows Version 19.12 or greater? - Do you have CVAD 1912 or greater.
CTX115637 Citrix Session Graphics Memory Reference describes how multi-monitor resolution is determined. Open the registry (regedit) and navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\vbdenum Increase the value of "MaxVideoMemoryBytes" REG_DWORD value to the above calculated memory. Reboot the VDA. Citrix Policies also control graphics performance.
Give the hive a name and click OK. Within the hive navigate to SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer and create a new key called Serialize. Create a new DWORD 32-bit value within the Serialize key. Give the value a name of StartupDelayInMSec and a data value of 0x0. Click File -> Unload Hive.
The Citrix Desktop Service failed to register with any delivery controller. The service will retry registering with controllers in approximately 17 seconds. Please ensure that at least one delivery controller is available for Virtual Desktop Agents to register with. Refer to Citrix Knowledge Base article CTX117248 for further information.
