Every time I use a VPN and disconnect from it my Wi-Fi router disappears from the Wi-Fi network list. This happens on my Android Pie phone and tablet.
I can see all other routers but not the router I was using. After I do forget the Wi-Fi and manually enter SSID and password it doesn't bring up the router. It comes back after a long time on its own.
This is not a problem with my Wi-Fi router because I can connect to it in my Windows 10 laptop and Ipad