First time set up, blinking yellow

If this is a new service installation / new move-in, the other end of the line has probably been disconnected from the Comcast feed. It's quite typical. You likely need a tech out to reconnect your premises to the active Comcast feed at the main splitter for the building / premises. If it's a multiple dwelling, you can try to get the owner / manager / maintenance person to do it. You won't be able to activate the service with the app if your line is not connected to the system. Good luck ! And please post back here with how things turn out.