DIAGNOSIS The Deco's 2.4 GHz network broadcast likely resumed before its internet connection was fully established. Many IoT devices fail their connection sequence if they can't reach the internet immediately.
FIX Power cycle your modem first. Unplug it for 60 seconds. Plug it back in. Wait for all its lights to stabilize. Then, power cycle your main Deco unit. Unplug it for 30 seconds and plug it back in. This ensures the correct boot order.
IF THAT DIDN'T WORK Your Deco's network name (SSID) or password may have reverted to an older setting. Check the Deco app to confirm your current network names. You may need to manually reconnect each smart device to the correct, verified network.
HEADS UP Smart devices have primitive network logic. If the reboot fix doesn't work, you will likely need to hard reset each stubborn device (using its own button) and set it up again from scratch in its manufacturer's app.