WiFi says connected without internet, but works fine I am connected to a school WiFi network and I am able to access webpages and my apps work fine, but Android says I am connected but have no network. The issue is that Android defaults to mobile data when it claims it isn't connected, which costs me money. I know that I am connected and have internet access, even when mobile data is turned off.

As of now, I have just been turning mobile data off in order to keep Android from defaulting to mobile data on that network.

I'm on a Pixel XL on Android 9.0 pie. The issue has existed since I got the phone (it was on 7.1 Nougat at that time)
I had a similar issue. I solved it by rebooting the router. You can also just restart the gateway.