Can you provide tips to extend an open WiFi network that requires sign-in after connecting? I tried using Tplink Ac750 as an extender, set it up, but when connecting to the router with my phone, I can't access the sign-in page to connect to the internet. It only shows that the router is connected to the WiFi network, but there is no internet connection. Is it possible to extend the network in this scenario, and if so, what are some tips to do it?