@David-TP thanks for the pointers on the use of Guest network. This is now resolved.

For anyone out there who faces this issue. I was using the WiFi Guest network for my wireless device. Seems like there's some isolation mechanism that prevents devices in that network to be able to reach wired devices connected to the Deco even if they are in the same subnet. If you instead use the Main Wifi network instead, wired and wireless devices can reach each other just fin.