When you are trying to use RDP in conjunction with Citrix Xenapp you might get the error message when connecting to full desktop via ICA or RDP on the terminal server, “the desktop you are trying to open is currently unavailable”
This is because by default, Citrix restrict the use of full desktop.
In order to allow “full desktop” access you have to create a Citrix user policy.
So open Citrix Appcenter –> Go down to Xenapp –> The farm –> Policies
Open the User tab, and choose the default policy and click edit.
And under ICA there you can enable “Desktop launches”
Incase you are using Remoteapps also you need to configure the “Launching of non-published programs during client connection” in order for it to work.