Hub Error: Connection to Qlik Sense engine failed for unspecified reasons

[Yoichi_Hirotake]

When using an app in the Hub, the message "Connection to Qlik Sense engine failed for unspecified reasons" is displayed.

Connection to the Qlik Sense engine failed for unspecified reasons. Refresh your browser or contact our system administrator
 

Accessing the Hub from a different URL, or directly on the server by addressing localhost, works.

Environment:

Qlik Sense any version 

Resolution:

There are various possible root causes for this issue.

• Websocket Connectivity
• Websocket White List
• Extended Security Environment Enabled
• Port availability 
• Further troubleshooting steps can be found at the conclusion of the article 

Qlik Sense Websocket Host White List

Add the URL used to access the Qlik Sense Hub to the Websocket Host White list of the virtual proxy.

• Open the Qlik Sense Management Console and navigate to Virtual Proxies. 
• Select the Virtual Proxy serving your hub
• Open the Advanced tab

The Host White List needs to include the URL the hub is being addressed with. 

For example, "qlikserver3.domain.local" needs to be added into White List of the virtual proxy if this is the URL used for accessing it.
It can be added using the full URL "qlikserver3.domain.local" or shortened to "domain.local".

General Websocket availability 

Verify that Websockets are supported in the infrastructure. 
See Qlik Sense Websocket Connectivity Tester on how to test Websocket connectivity. 

Extended Security Environment Enabled

• Locate the virtual proxy you are using to access the hub (https://your-server/your-vp/hub) in the QMC (if it is just https://your-server/hub, then you are using the Default virtual proxy
• Open the Qlik Sense Management Console and navigate to Virtual Proxies. 
• Select the Virtual Proxy serving your hub
• Open the Advanced tab
• Under Advanced is "Extended Security Environment" checked?
• If YES, then this may be expected behavior.

When "Extended Security Environment" is checked, an user can only access Qlik Sense with ONE device. Verify with your administrator if there is a 3rd-party tool which is logging on as this user, as this would kick the user out of their session. 

Further Troubleshooting and possible root causes

Alternate Cause

• Server is behind a NAT server (network address translation) in a network that is not correctly configured

Troubleshooting Steps 

• Verify if the issue is seen locally as well and not through a proxy. If the issue is only noticed while accessing Qlik Sense through a 3rd party proxy, the proxy may not be configured to permit websockets.
• Verify that general service connectivity between Qlik Sense services is OK. Issues that can prevent service communication include ports not available (see list of ports), or certificates corrupted (see How to recreate or just delete certificates in Qlik Sense on how to recreate certificates). 
• Check the Knowledgebase for an article further narrowing down your symptoms to a specific issue/product defect. Examples include:
  • Connection to the Qlik Sense engine failed for unspecified reasons randomly on the hub
  • Connection to the qlik sense engine failed for unspecified reasons when connecting to the Hub only