DIAGNOSIS The printer lost its network connection. This happens after a router reboot or if credentials changed.
FIX Press and hold the Wi-Fi button on the printer until the lamp flashes blue. This resets network settings. Use the Canon PRINT app on your phone to guide you through reconnecting to your router.
IF THAT DIDN'T WORK Your router may be blocking it. Temporarily disable the router's 5GHz band. Connect the printer to the 2.4GHz band only.
HEADS UP Do not use WPS push-button method if your router has it. It's less reliable. Use the standard SSID/password setup.