Hi, some of the logs on %ProgramData%\QlikTech\ folders can give more detail on the error.
I guess it may have something to do with SSL. You can follow this article to enable SSL: https://support.qlik.com/articles/000004039
It will be better to check the logs looking for the error to confirm if it has something to do with SSL, but also you can try to enable and if it's not working set again the .exe.config files as they where before modifciaction and look for the logs to get more info about the error.