If you get a "server not found" error when you try to access keezel/ in Safari, it's because your device decided to connect to another WiFi network without notifying you.
You need to check if your device is still connected to the Keezel wifi network, reconnect it if it's not and try again.
This might happen more than 1 time during the Keezel configuration process, so you'll need to regularly check if you're still connected to the Keezel.
Alternatively, you can have your device "forget" all the saved networks. Here's how: https://www.imore.com/how-forget-wi-fi-network-your-iphone-and-ipad