You can see the required ports for Qlik Sense here: Ports.
Port 80 (HTTP) is one of the required ones as seen in the list. As for how to enable them: You would need to get in touch with your network administrator(s) so they can make the required adjustments or help you locate where the port is blocked.
For external users as client to access Qlik Sense Server with Browser, the ports port HTTP 80, SSL 443 are only necessary. And they should make sure the ports open.