Found this post from 2015. Having same problem. This happens everytime my children get access to koalasafe via a time extention or schedule. All settings appear correct and devices show that they are connected to koalasafe Wi-Fi but all apps that require internet access show ‘no internet connection’. Only way to fix is turn off devices and koalasafe and turn back on (sometimes more than once). Koalasafe is connected to house modem (other devices not on koalasafe have internet access directly from this modem) via Ethernet cable and 2 green lights and 1 red light are showing.
Consistantly no access to internet although ipad showing connected to koalasafe wifi and app settings showing access allowed