DIAGNOSIS The Deco is booting up but cannot acquire an IP address from your modem. The modem likely booted faster and locked out the Deco's request.
FIX Power cycle in correct sequence. Unplug both the modem and the Deco. Wait 30 seconds. Plug in the modem only. Wait 2 full minutes for it to fully initialize. Now plug in the main Deco unit. The light will blink blue, then turn solid blue when connected.
IF THAT DIDN'T WORK Your modem may have issued a different IP. In the Deco app, go to Internet Connection. Try releasing and renewing the DHCP lease. If options are greyed out, you need to wait for the modem's DHCP lease to expire, which can take hours. The power cycle sequence is the faster fix.
HEADS UP Frequent power outages can corrupt Deco firmware. If the unit stays blinking blue for over 10 minutes after a correct power cycle, a factory reset may be required. Use the reset button on the back.