Apple TV 3rd generation impossible to reset wifi password
I need to start using an Apple TV 3rd generation, but it has remembered an old password to my wifi network. It seems to be impossible to make Apple TV forget this password. It always tries to connect, and fails. The window that would let me enter my password doesn't open.
I have tried resetting to factory settings, directly on the Apple TV as well as via my macbook connected to the Apple TV. Didn't help.
I have two wifi networks, my own and a guest network. I can connect to the guest network, but not to my own network, so I guess it's not linked to network security, because both networks use the same security settings.
When Apple TV tells me it failed to connect, I have retried lots of times, it doesn't seem to get out of this loop.
Any help or tips would be appreciated.