Why is my iPad unable to determine location with some hotspots?
If your iPad doesn't have GPS hardware (available only with cellular models), iOS on it uses an online geolocation service to try determine the location.
One of the ways the geolocation services tries to do this is by trying to determine the location of the wifi you have connected to. This works well only if the location of wifi is already known - like cell phone towers, or public wifi hotspots, or wifi routers whose location is already known because of other devices (with GPS) that have connected to it etc. Generally, if you are connected to a cellular data, some cellular providers can also provide limited GPS data but this is also not consistent.
In other words, if your device doesn't have built-in hardware for GPS, trying to determine your position through other means are somewhat unreliable. And that is what you are experiencing.