X60 cannot connect to internet
Just picked up a Deco X60 3-pack. I can successfully create a mesh network (one Main and two slaves) only if the main Deco is connected to my existing, complete network: internet -> modem -> old router -> Main Deco -> slaves. I can connect devices to the Deco's wifi network (separate from my old router) and everything works fine everywhere.
If I remove my old router and just go Internet -> Modem -> Main Deco....no slaves or other devices to complicate the network....the Main Deco goes solid red on the light. It cannot connect to the Internet. Modem lights are all good. Wired internet direct from the modem is good. But, still, solid red on the Deco.
I have tried a number of various power cycles on both network equipment and wireless devices. Deco is set to Dynamic IP. I can still connect to the Deco via the Deco mobile app, but I cannot get it to see the Internet. It's almost like it can't resolve the WAN for itself when connected directly to the modem - apologies if my terminology there isn't correct. I have also tried resetting the Deco and even trying one of the other units in the pack as the Main Deco - but each time I create and setup the network, I get the solid red light.
What settings should I be looking at, to troubleshoot? What am I missing on this? I don't have any reason to suspect that there is hardware issue. I am almost positive I am missing a setting or a step somewhere.
I appreciate you taking the time to read my issue.