May be it's Proxy issue:
The site I was installing at uses a Proxy Server for Web access, and even though Sense was installed on the local domain, and the bypass proxy for local addresses was ticked, it seemed that requests were still going via the proxy and were therefore failing.
Adding a manual exclusion for the Sense site in the Advanced settings under the Proxy settings (in the IE, Settings, Connection options) solved the issue.
I am thinking this is something to do with their network or corporate security policy. Do you know if we have to allow/open
certain ports on their end as well?
Check these ports 443,4244,80, 4248. I though these needs to be opened on server side and not one the client side.
It is wired that Qlikview works fine for this customer and not Sense. I know there is no Webserver with sense and everything is through Websockets.
May be firewall issue like below:
We figured out our problem. We are running Avast anti-virus on our Macs. Not sure why, but Avast seems to be causing Qlik Sense to lose it's connection after about 2-3 minutes. Once I added our Qlik Sense URL to the exclusions list in Web Shield, it stayed connected. We run Avast on our PC's too, so not sure why we don't have this same issue.
Check this:
https://community.qlik.com/thread/167783
