Issue was reported when VDA was upgraded from 7.13 to 7.18.
When an ICA session was launched, mapped drives from VDA does not show up in ICA session.
Check the value of registry at Client.
Reg Value: HKLMSoftwareWOW6432NodeCitrixICA ClientEngineConfigurationAdvancedModulesClientDrive : NativeDriveMapping
It changes the value to FALSE from True, after the session was launched.
Procmon traces shows Icaconf.exe was changing the value from TRUE to FALSE
Icaconf.exe is a tool used to populate the registry based on the INI files in the “Configuration” directory.
Configuration directory of Citrix Receiver has multiple ini files.
A file named Module.ini has the value NativeDriveMapping = FALSE.
Change the value from FALSE to TRUE in the file.