Unfortunately, this took a lot of research.  What neither TP-Link nor Google Fiber will tell you is that you have to change the MTU value.  The default 1500 will not work.  The smallest MTU for IPv6 is 1280.  Start with that and you can increase the value until you get to the highest value that will work.  You figure out the highest value by pinging a trusted website with increasingly higher MTU values until you start losing packets during the ping test.  Fun way to spend a weekend.  If someone has already figured out what that maximum MTU value is for the ER605 router and Google Fiber, let us know.  I just have mine at 1280 right now until I feel like spending the time to try higher numbers.  Hope this helps somebody.