We have single node qliksense setup on server. We were able to open hub using http,but suddenly on one day we were unable to open the hub using http. We got page cannot be displayed error. At the same time we were able to access the hub using https.
Later after restart of all the services ,hub was accessible using http also.
You might have enabled both HTTP and HTTPS, but issue might be because some other webserver like (IIS/Apache etc) may be running in background and blocking your 80 port. After server restart it would have allocated again to Qlik sense. you can check Task Manager(resource monitor) which will show the Applications using the port 80(http) / 443(https).
We just restarted the services not server ,I am just thinking will it be possible for other service to occupy the same port when one service (Qliksense proxy) is already running . We don't have apache/IIS installed on server