Recently, I needed to connect to an open WiFi-hotspot with my laptop (with MacOS) for internet connectivity. For some reason, the captive portal of the network did not show up. Hence, I was not able to reach the web and secure my connection with a VPN.

First, I checked the status of the network connection of the wireless network adapter. I was connected to the network and received a local IP adress, also the IP of the gateway seemed ok. I was able to ping other devices in the network and also the gateway. I tried to launch the captive portal in a browser since I got the URL from another device which was successfully connected.

After some online research, the issue was to be found in the DNS settings of the network adapter in MacOS. The Cloudflare DNS resolver 1.1.1.1 was listed explicitly, and the device was not able to reach it. I deleted the entry, and the DNS IP from the local network appeared immediately. Finally, the captive portal popup was brought to live and I could access the internet.