After well over a year of major issues it suddenly wants us to sign in to the WiFi network?

[Marielittle]

Our WiFi is suddenly, on every device, telling us to "sign in to WiFi network" which first of all makes no sense. We're not a business or something and we've never had to sign in before. When we do click sign in it asks if we're a new customer or existing
When we click existing it then says "webpage not available"

[NFtoBC]

Can you provide a bit more information? 
Your modem should require a login and password to access the network. Usually, your device remembers this login, and automatically reconnects each time you arrive home.