but filling out the details causes the same dialog to reappear, over and over again. Eventually I gave up, but had to hit cancel a bunch of times to get it to go away. I gave it a couple more goes and got the same behaviour every time. I double checked my username and password combo and I'm sure they were correct so I'm not sure what else to try.
I suspect it's because of macOS 10.12. I didn't see the dialog in the few 10.13 computers I tested this on. But it could still be something else.
Is your user account the sole admin account?
Does the window shake after you provide the username and password or does it simply disappear and reappear again? Can you try providing an incorrect password and see if it shakes?
Can you run this command in Terminal and see if the window pops up again? (assuming your default network interface is Wi-Fi)
When running
I get a macOS system dialog like
but filling out the details causes the same dialog to reappear, over and over again. Eventually I gave up, but had to hit cancel a bunch of times to get it to go away. I gave it a couple more goes and got the same behaviour every time. I double checked my username and password combo and I'm sure they were correct so I'm not sure what else to try.
macOS: 10.12