My device is connected to WiFi but I have no internet access
In many administrated networks there is a firewall which blocks access to unknown addresses and different types of network traffic. For example the firewall may be blocking any VPN connections which will cause you to have no internet connection.
These types of networks can be found in places such as - work offices, universities, schools etc.
In these networks the network admin must add these IP addresses to the white-list firewall rules: