Forgive me, but I have to state all suspicious causes:
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Just as an update in case someone faces the same problem and reads Michael's post. You will notice in the last bullet point he mentions
This is actually only relevant if you have a proxy and as you can see from his screenshot, the option to bypass proxy would normally be greyed out, so it is not possible to check that box.
However, in my case "Automatically Detect Settings" was checked, and once I removed it and launched QlikSense, the error was gone and everything worked fine after that.
Hope this helps others.
*I did the repair-installation as suggested but then I received this message below.
* I also tried to adjust the network settings but then I couldn’t access internet at all.