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

[wireless]

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"

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