The following event is displayed in the event viewer:
 
First error message:
Log Name:      Citrix Delivery Services
Source:        Citrix Store Service
Date:          7/22/2016 12:05:09 PM
Event ID:      4003
Task Category: (12346)
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      StorefrontSrv.Contoso.com
Description:
All the Citrix XML Services configured for farm SMSTORE failed to respond to this XML Service transaction.
 

Complete the following steps to resolve this issue:

1. Verify that the correct XML port is configured on the XenApp/XenDesktop server.

2. Make sure that StoreFront is using the same XML port as XenApp/XenDesktop server.

3. Make sure that StoreFront can communicate with the XenDesktop/XenApp servers.

4. Disable Windows firewall on the XenApp/XenDesktop and StoreFront servers.

5. If you are load balancing the XML brokers, create a test site and add only one XML broker.

6. Increase the value of the serverCommunicationAttempts attribute to set the number of unsuccessful communication attempts before the server is considered to be unavailable (Default is 2). Use the communicationTimeout attribute to set the time limit in seconds for a response from the server (Default is 30).

   1. Use a text editor to open the web.config file for the store, which is typically located in the "C:\inetpub\wwwroot\Citrix\storename\" directory, where storename is the name specified for the store when it was created.

   2. Locate the following element in the web.config file:
      <farmset ... serverCommunicationAttempts="2" communicationTimeout="30" …>

   3. Change the values of serverCommunicationAttempts="6" communicationTimeout="60"

7. When a StoreFront to XenApp/XenDesktop server request times out, StoreFront ignores that server for (by default) 1 hour. When all servers in a single XenApp/XenDesktop site have failed in this way, the time is reduced to (by default) 5 minutes. Reducing this 5 minute to 0 minutes might resolve the issue.

   1. Use a text editor to open the web.config file for the store, which is typically located in the "C:\inetpub\wwwroot\Citrix\storename\" directory, where storename is the name specified for the store when it was created.

   2. Set allFailedBypassDuration to "0".

   3. If there are more than 1 XML server then set loadBalance to "on" in the <farm> elements. This should better spread the load between the XenApp/XenDesktop servers which may reduce the problem.

   4. Change the values of pooledSockets to "on" in the <farmset> element. This may speed-up connections to the XenApp/XenDesktop servers and reduce the likelihood of timeouts.