UPDATE!

Ok, I know replying to my own post typically isn't cool, but I came across something that bothers me.

NONE of the devices in the living room are connected to the Deco, with the exception the mobile phones.  My wife's laptop, as well as our landlady's laptop are NOT connected.  In the Deco app, they still showed up, but as Offline.

Looking at another thread I found here (Link) I tried setting a static IP address on the Printer, and it seemed to be working (Deco sees it again).  I can ping it from my android phone, as long as it is connected to the Deco AP, but not if connected to the office AP.   I cannot ping it from my desktop which has a wired connection to the main wi-fi router in the office.   None of the laptops could talk to it from the living room.  It appears they were connected (barely) to the office AP. 

Once I fixed this on the laptops, specifically my landlady's laptop (switched the AP it was pointing to by default), it all worked.  

The only thing I still cannot fathom, is why I cannot ping the printer, from MY desktop.   It is all one network, same name.  

So, if I really needed to, I would not be able to print to the living room printer (my landlady's printer) if I needed to.

Eric the Grey 

  @EricTheGrey To assist you in troubleshooting, please supply us with an accurate picture or description of everything in your network. 

Everything from the Internet demark (the wire coming in for the Internet), to each and every connected device. 

Show Deco's with the backhaul connections and the relative rooms that each device is located. 

  @DAServices   Hi.  I can give you an example, but it is not to scale.  

Legend

1. Fiber converter.  Connected to the main internet wi-fi router. 

2. Main internet router. 

3. Desktop connected to wi-fi router via Ethernet

4. Deco Wireless router.  Connected to Internet wi-fi router by Ethernet.

5. Laptop 1

6. Laptop 2

7. Wi-fi Printer (HP Office Jet Pro 8600).  

There is also a TV, and DirectTV box connected to the Deco sitting at the same location.  The Deco sits directly next to the TV.

Note that the hose is small, but old.  The walls consists of what amounts to chicken-wire with plaster over it.  This serves to block most of the wi-fi from the office, but not all.  Reception in the living room is very spotty, which was the reason for putting the Deco in there.  

Regarding "backhaul connections" I'm no network guru.  My strength lies in PC hardware and software.

While typing this, I started wondering about the two different devices providing differing IP addresses.   My desktop, for example, has a 169.168.0.x IP, while devices connected tot he Deco all have 192.168.68.xx IP addresses.   

Could that be the problem?  If so, how do I change it on the Deco to mach my main router?

Eric the Grey

  @Heidi_Alp That seems to have done the trick, although not without a glitch.

After switching to AP mode and rebooting, it failed to restart properly.  The light remained red for a long time (I even took a shower while I waited).  

Ended up having to power-cycle the device to get it back, but it came up in AP mode, and now everything I tested is communicating properly.  I can even ping my printer.

Thank youf or your assistance.  These are great devices, IMO (once you know what the he** you're doing with them, LOL). 

Eric the Grey