fire tv cube gen 3

Just upgraded to Amazon Fire TV Cube Gen 3 mainly for Xfinity cable TV control via the Amazon remote.  However, during setup when asked for providers in my ZIP Code (95066), Xfinity is NOT listed.  Comcast/Xfinity has been here for decades, so it's not new.  I have an XB7 box. 

Amazon tech support suggests it's an Xfinity problem. 

Help!