Unable to open published applications from XenApp 6.x and one of the following error messages might be displayed:

Error 1

“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 Citrix administrator."

Error 2

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

External connections through the NetScaler fail with a "protocol driver error" while internal connections to the same XenApp server are still successful.

Error 3

“Please verify your user name and password and try logging on again. If you cannot logon, contact your help desk.”

Event logs on Web interface might display:

“An error occurred while attempting to connect to the server <server-name> on port <port-number>. Verify that the Citrix XML Service is running and is using the correct port. If the XML Service is configured to share ports with Microsoft Internet Information Services (IIS), verify that IIS is running. This message was reported from the XML Service at address. The specified Citrix XML Service could not be contacted and has been temporarily removed from the list of active services. [Unique Log ID: 96e89a1b]”.

“All the Citrix XML Services configured for farm <farm-name> failed to respond to this XML Service transaction. [Unique Log ID: aa9d31ab]”

Error 4

Error: An error occurred while making the requested connection.

Error 1 - Resolution 1

Consider one of the following resolutions to resolve the errors:

Complete the following procedure to ensure XenApp 6 policies are configured correctly:

1. Open Citrix Delivery Services Console.

2. Click Policies.

3. Navigate to the Computer tab and Edit the unfiltered policy.

   

4. Click Next in the Identify your policy window.

5. Review your policies and enable the following settings, as displayed in the screen shot:

   • License Server Host
   • License Server Port
   • XenApp Product Edition
   • XML Service Port
   

6. Save the Policy.

7. Run gpupdate /force from server command prompt.

   

Error 1 – Resolution 2

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

Error 1 – Resolution 3

If an advanced load evaluator is used, change to a default load evaluator based only on user load and load throttling. There could be a problem with performance counters that an Advanced Load Evaluator relies on.

Error 2 - Resolution 1

Verify RDP and ICA listeners network adapter configuration.
Important: If only one NIC is allowed for ICA traffic based off of network rules, firewalls, etc. then bind specific network adapter to the ICA listener.

1. Open Administrative Tools from the XenApp Server(s).

2. Browse to Remote Desktop Services.

3. Click Remote Desktop Session Host Configuration.

4. Select RDP listener.

5. Right-click, navigate to properties and verify all network adapters are selected.

   

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

   

   

Error 2 - Resolution 2

Check the XTE Service status. If Session Reliability is enabled, XTE service is required to broker the connection to the XenApp Server.

Error 2 - Resolution 3

Restart IMA service after the server is moved to the Worker Group that has Session Reliability enabled to resolve the issue.

When a server is booted and already placed in the correct Worker Group, where the Session Reliability is enabled, and the XTE service is not started, check the order in which the policies are applied. Ensure that the policy which enables the session reliability is set first (lower number in AppCenter console).

You can also try disabling the NetScaler global setting USIP (Use Source IP) mode.

Error 3 - Resolution 1

Complete the following procedure to ensure that you have registered the correct port on the XenApp 6 server(s):

1. Open Services.msc from the XML broker(s) (XenApp Server).

2. Ensure the Citrix XML service is started.
   Note: If the service is not started, register the correct XML port on the server and restart the service.

   

Error 3 - Resolution 2

Complete the following procedure to check that the Web Interface XML configuration is set properly:

1. Open Citrix Web Interface Management.

2. Select XenApp Web Sites.

3. Click Server Farms.

   

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

• Verify that the correct XML port is entered in XML Service Port.

  

Error 4 - Resolution 1

1. Go to the registry key HKLM\Software\Wow6432node\Policies\Citrix on the ZDCs and verify if IMA key which contains the licensing settings are missing.

2. If they are missing then export the same key from a worker server and import it to the ZDCs and reboot.

Note:
Also, run qfarm /load to see if logons are enabled or not. In case logons are Prohibited, enable the logons from the app center.
To enable logons do the following

1. Launch App center, and browse to 'Servers' node under the farm
2. Right click on the server for which logons are prohibited 
3. Click on 'Other tasks' and then click 'Logon Control'
4. Click on 'Allow Logons and reconnections'

After this, recreate LHC by running the command 'dsmaint recreatelhc' (make sure IMA is stopped before and start after LHC has been recreated). Also make sure that the applications are published to the server in questions by verifying Application Properties.

 

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Problem Cause

Several configuration options might prompt these errors. There may be important XenApp connection ports (1494, 2598, etc.) that need to be opened on the firewall. Refer to CTX101810 – Communication Ports Used By Citrix Technologies for more information.

Error 1: The first error might be caused by a load evaluator, corruption in the Farm Database, an issue in IMA, Licensing, an overloaded server, and so on.

Error 2: The second error is related to an issue in the network stack. This could be an issue with the ICA listener or an issue in the XTE Service.

When session reliability is configured in the unfiltered policy to be disabled, but for a specific worker group they have a separate policy which enables the session reliability for that worker group.

After the server has started and the server is moved to the Worker Group where the Session Reliability is enabled, the XTE service is not started and users can connect to the server (using port 1494, not Session Reliability) but when the gpupdate has run this fails and the users receive a protocol driver error. When a policy change occurs and a gpupdate is run, the content of the httpd.conf file does not change till the IMA service is restarted.
So the protocol driver error connection issues are seen, when the IMA service is restarted the httpd.conf file gets updated and the XTE service is started. This behavior is by design and work in this manner. 

Error 3: The third error is likely a configuration problem between the Web Interface server and XML Broker.

Error 4: ZDC servers ran out of disk space on system drive, which might have eventually caused the Citrix GPCSEs to fail in creating the licensing related keys in registry.

This artcile contains informattion to troubleshoot when unable to launch published applications from XenApp 6.x.

There can be numerous reasons for an application launch to fail. This is not an exhaustive list, however it provides some guidance on common errors. In case the error occurred is not listed in this article, or failure in implementing any of the preceding procedures, collect a CDF trace and contact Citrix Support for further analysis. Refer to CDF Tracing via CDF Control - CTX111961 – CDFControl.

Note: The ICA listener configuration described in this article only applies to XenApp 6 / Windows 2008 R2 x64 version.

You may also refer to the Citrix Knowledge Center Highlights: App Virtualization & VDI (July Edition)