@Mattpm 

Archer won't joint Deco mesh.

You have two options: keep Archer as router and configure Deco to run in Access Point mode, or put Archer in bridge mode and run Deco in Router mode. What’s the difference between Access Point mode and Router mode on the Deco?

My personal preference is to run Deco in Access Point mode, but I bought Deco mesh (two M9 Plus and two M5) specifically to improve WiFi coverage in my house, and use it for nothing else. If you use Deco mesh Router mode specific features, it makes sense to just bridge Archer.

  @Alexandre. 

Thanks, that makes sense.

I am taking advantage of some of the features on the deco m9 mesh system so ideally, would like to continue running it in mesh mode.

With my old ISP, I didn't need to enter any credentials however, with the new one I do.  Any ideas where I can enter those connections within the Deco application?  I've been looking all through it and can't find it.  Or do I need to do a factory reset the Deco units and reconfigure them all again?

Also, with putting the Archer VR600V into bridge mode, is the easiest way, just to use the quick set up wizard?  I've taken a backup of the configuration.