Hope you are doing well!
We clearly see the issue here with the tunneling and giving an error message "ERR_TUNNEL_CONNECTION_FAILED" So you are trying to access it from the external IP address which routes to your firewall and then through internal routing rules, it should reach to Qlik sense.
Does Qlik sense server has public IP address or private IP address?
Usually, we had seen such issues when required ports are blocked in the environment. You should try an external resolvable name so that you can try accessing it because you are not directly hitting to Qlik sense server if that has an internal IP address.
It is working fine when you try internal IP address on which Qlik sense is installed and it is making a direct connection to that whereas accessing from outside would eventually go VIA firewall and once it does not find the right address and ports are blocked then it should not open a page for you.