After aeons of complaints about the wifi deadspots I've bitten the bullet on a mesh system.  I've chosen the COVR AX for the number of wired devices I can plug into each node. 

But no matter what I do, using the setup app, I cant get the mesh node to connect to the internet through the supplied Vodafone HG659 router.  I can only get an internet connection by plugging the mesh node into the ONT (replacing the router) despite the setup process clearly showing it plugged into a LAN port on the router.  

I've tried it with ethernet from router to WAN port on the mesh node, from router to LAN port on the mesh node.  It wont connect through the router at all.

Am I missing something obvious?  Replacing the Vodafone router is not my preferred option given the loss of the home phone security blanket for some household members......