If you're having trouble connecting to the Call of Duty: Modern Warfare, you should first check Call of Duty: Modern Warfare Server Status. If the status indicator for your platform is not green or an alert is present, you might encounter connectivity issues until service is restored and fully operational.

If you can't connect to a Wi-Fi network that you could connect to before, it's possible that the network settings might have changed or the profile is corrupted. To fix this, remove (or "forget") the network connection, then reconnect to the network.