@Brewster 

What you need to do is configure Deco mesh to run in Access Point mode. This should fix WiFi printer access. I also expect your Bell router will again show your devices with familiar nicknames you gave to them.

See How to set up Deco to work in Access Point mode

  @Brewster Thanks for the quick reply. I configured as a router since it was recommended and had more function. I will make the change and let you know. I do need the printer to be shared. The way I have it is there a way I can tell from the app.which of the 2 Deco units any of my devices is using? I ran OPTIMIZE but it made no difference (I bought Deco because the Bell signal was not reaching my deck outside. Now even as a router it does. I also have a wireless WIFI speaker on the deck which no longer works configured as router.)

Brewster

  @Alexandre. Just to clarify, is configuring as AP the ONLY way to share a printer? I like the Router config. features. Need to know if I can find a Windows/PC problem (compare the 2 PC Windoes configs & options myself) for my wife's PC or is it a Deco design characterisitic. Seems to me single printer sharing is a very common household requirement.

  @Brewster 

You should be able to share printer in Deco Router mode. It is, indeed, common household requirement. Conceptually, Deco mesh in Router mode is single WiFi router with very strong WiFi signal. 

The reason you came here is because something going on with your home network and Deco mesh that prevents printer sharing. There may be multiple possibilities why sharing doesn't work. Changing Deco mesh to Access Point mode eliminates one or two of them.

In Access Point mode, Deco is not much more than WiFi traffic pass-through. As explained in What’s the difference between Access Point mode and Router mode on the Deco? If you can't make printer sharing work to your satisfaction even with Deco in AP mode, you may wish to return that product and try WiFi mesh from different brand.

  @Brewster Thanks again Alexandre for your candid reply. I will try moving the PC without access to the printer down beside the other PC so they share the same Deco unit. If that works i will let you know.

  @Brewster FYI I now have my shared printer accessible to both of my PCs on Deco as a Router. Access Point was not necessary. The problem appeared to be with the printer config. in Windows 10 on the one PC after I set up Deco. I had to delete the printer queue; remove the printer from Settings/Devices/Printers and Scanners; then re-add it. 

Thanks for all the feedback.