Unable to Launch Published Applications from XenApp 6

Symptoms

You are unable to open published applications from XenApp 6 and receive the following error messages:

“Cannot connect to the Citrix XenApp server.
The Citrix XenApp servers are reporting full load and cannot accept your connection at this time.
Try to connect again after a few minutes. If you continue to receive this message, contact your Citrlx administrator.”

“Unable to Launch your application, Contact your help desk with the
following information: Cannot connect to the Citrix XenApp server.”

“Protocol Driver error”

Cause

Several configuration options might prompt these errors.

Consider one of the following solutions below to resolve the errors:

Resolution 1

Check that the Web Interface XML configuration is set properly.
Open Citrix Web Interface Management.
Select XenApp Web Sites.
Click on Server Farms on the far right of the window pane.
Click on Edit:

a. Ensure that the correct XML broker(s) are listed under server.

b. Verify that the correct XML port is entered inside XML Service Port.

Resolution 2

Ensure that both RDP and ICA listeners are not set to a specific network adapter.
From the XenApp Server(s) open Administrative Tools.
Remote Desktop Services
Remote Desktop Session Host Configuration
Select RDP listener:

Right click go into properties and verify all network adapters are selected:

After verifying all Network Adapters are selected, review the ICA adapters (only applies to XenApp 6 / Windows 2008 R2 x64). Click on Start > All Programs > Citrix > Administrative Tools > ICA Listener Configuration.

Resolution 3

Ensure XenApp 6 policies are configured correctly.
Open the Citrix Delivery Services Console.
From the left pane, select Policies .
Select Computer from right pane and edit the unfiltered policy.
When the Identify your policy window opens, click Next.
Review your policies and enable the following settings:

a. License Server Host

b. License Server Port

c. XenApp Product Edition

d. XML Service Port

Save the Policy.
Run gpupdate /force from server command prompt.

Resolution 4

Ensure that you have registered the correct the port on the XenApp 6 server(s):
From the XML broker(s) (XenApp Server) open Services.msc. Ensure the Citrix XML service is started.
If the service is not started, you might need to register the correct XML port on the server and restart the service:

Resolution 5

Always clear Local Host Cache on all servers in farm to ensure a fresh copy of the datastore subset is applied to the XenApp and Zone Data Collectors.

Though IIS and XML can share the same port by default during an initial installation of XenApp 6, it is recommended as a best practice to assign a different port (for example: 8080) to XML