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"An error occurred Connection lost" or "Bad Request the http header is incorrect on Qlik Sense Hub"

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"An error occurred Connection lost" or "Bad Request the http header is incorrect on Qlik Sense Hub"

The following errors may be experienced when accessing the Qlik Sense Hub:

An error occurred Connection lost
Connection to the Qlik Sense engine failed for unspecified reasons
Bad Request the http header is incorrect

Log files may show:
500 Internal error: unable to route websockets request to the following URL, wss://SERVERNAME/PROXY/sense/apps


From Proxy > Trace > Audit:

18 20191107T180810.403-0500 WARN servername Audit.Proxy.Proxy.Core.Connection.Validation.ConnectionDataValidator 25 b3fbafe9-7fba-4cca-8113-587ff923c31e domain\user Http request Host is not allowed: host.fqdn.local 0 c986fb07-a8b8-49c1-9e5c-ac7f56a303a1 ::ffff: {header} 21b23e5e635767f3b18a1adbf9f7b62e97100f04

Refreshing the page does not resolve the issue...

An error occurred
Connection lost. Make sure the Qlik Sense is running properly. If your session has timed out due to inactivity, reconnect to Qlik Sense to continue working.


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400 Bad Request
The http request header is incorrect


  • Qlik Sense Enterprise, all versions



The "Connection lost" error message commonly occurs when:

  • Qlik Sense Hub is accessed using a different address than the one registered as the default DNS name / Fully Qualified Name of the machine. As an example, when using AWS or similar environments, the internal registered DNS name is not the same as the external facing address
  • Web sockets are not supported in the environment 



This is a general connectivity / websocket related error. It can have a variety of root causes.

I. WebSocket support


Qlik Sense requires WebSockets to be enabled. Third party proxies/reverse proxies or firewalls may not be configured correctly to allow Websocket traffic. Verify if this technology is enabled by navigating to https://websocketstest.com/ from an affected client.

If WebSockets are not available between client and the Qlik Sense server, the Qlik Sense Hub cannot be used.
For directly testing the Qlik Sense server itself, use the Qlik Sense Websocket Connectivity Tester.


II. The address being used when accessing Qlik Sense Hub must be added to the Host White List in the proxy

For detailed instructions, see How to configure the WebSocket origin white list and best practices.

To add an address to the White List, perform the following steps:

  1. In Qlik Management Console, go to CONFIGURE SYSTEM -> Virtual Proxies
  2. Select the proxy and click Edit
  3. Select Advanced in Properties list on the right pane

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  4. Scroll to Advanced section in the middle pane
  5. Locate "Host white list"

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  6. Click "Add new value" and add the addresses being used when connecting to the Qlik Sense Hub from a client
    • IP address:
    • FQN: myqlikserver.company.com
    • (Third party web-portals being used to re-direct users to the Hub)
    • etc...
    NOTE: An entire domain can be white listed by adding company.com into the white list. This will white list all other addresses within that domain, such as myqlikserver1.company.com, myqlikserver2.company.com, etc.


III. See the following article for additional guidance:

Hub access times out with: Error Connection lost. Make sure that Qlik Sense is running properly 


For assistance in troubleshooting issues with Qlik Sense Hub connectivity and much more, join Qlik community; Connect and learn from over 60.000 active users, find answers, and discover best practices and tips and tricks.

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Last update:
‎2021-02-10 05:54 AM
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