I had 2 problems and I have resolved them both.
1) I moved to a new house, and acquired a new ISP, Xfinity. Initially I couldn't get connected to Xfinity. Xfinity's cable modem is also a wifi router, and there was no option in the setup for using a non-Xfinity wifi router. Several articles that I read suggested changing a setting on the Xfinity router to "Bridge Mode enabled". This did not work for me. Finally I created a wifi network in Xfinity, then deactivated it. I had to login to the Xfinity router to do this, http://10.0.0.1.
2) Next, my 2 child nodes would not connect. Finally I hardwired them to the parent router (one-at-a-time). This forced them to factory reset, which took 10 - 15 minutes. Solid blue light indicates that node is in the process of resetting. When it starts flashing, it is complete. Once this was done the Google Home app was able to find the nodes and I could complete the setup.
If anyone has had a similar problem I would like to hear how it was resolved.
Thanks for sharing your experience. Sometimes things can get a little tricky in setup, and finding a solution isn't always so straightforward or simple. It looks like you really did your homework on this one. Also, you sharing your experiences helps our community resolve their own hangups and even informs our teams internally.
As you have a resolution on this one, I'm going to go ahead and close the thread but keep it available for all to search and read.