@Riley_S I just purchased a new Deco AX3000 X55 system and was disappointed to run into this problem.   It really shouldn't care what the MAC address is.  I was using Google WiFi mesh, so I entered the Google Wifi wireless MAC address into the DECO and it finally got internet access.    (Interesting that I had to try 3 options to enter the MAC address - without separators, with colons, and finally with dashes.  It kept telling me the address was invalid until I used dashes, which is unlike anywhere else I have seen MAC addresses.)  Anyway, it finally got internet access, but could not do DNS naming resolution.   My other routers automatically pick the DNS servers up from Comcast when registering.  I figure that I could enter DNS servers somewhere to fix this, but then I also saw that the Guest network cannot be named.    I have all of my IOT devices on a named guest network COLORNEW.  The DECO only supports a name of GUEST.   I am NOT going to reconfigure all of my smart switches and sockets, which would be required to change the name of the network they are on.   So I am returning the units.