Apple has routinely confused its users with the site captive.apple.com, which appears in a distinct Wi-Fi connection window that acts as a frontmost overlay in iOS, iPadOS, and macOS that you have to respond to. As I described back in 2018, Apple uses this website to test whether the Wi-Fi network to which you’ve connected has a direct internet feed or there’s a login or other portal between you and the internet.
Recently, however, a reader had this name appear while they were connected to their home ISP. The Wi-Fi login window showed captive.apple.com on the first line within the title area, the name of their ISP in the second line, and a form labeled “USER LOGIN” in the body of the page.
I advised them to contact the ISP, which ultimately had to remotely reboot the broadband modem with built-in Wi-Fi that formed their home network. The login then disappeared. So if you run into the same problem, call your ISP and ask them to remotely reboot your broadband modem.
Read more at Macworld.com