why is ethernet port is flashing on new Xfinity modem?

@Sowens

thanks for reaching out to us as a customer myself I always like to make sure my services is working as they should be if you went through the activation process on the awesome Xfinity app and got your services up and running where you're connected via Wi-Fi then the modem is activated correctly and your services are working than it does sound like that maybe you don't have the Ethernet cable into the wrong  port on the back of your modem.  Are you sure you have the Ethernet cable in the right port and not in the Tel port that is used for Vice services? When the Ethernet cable is connected to the right port and your services are working it should blink green blinking orange would mean that either it's in the wrong port or possibly there's an issue with your Ethernet cable can you please double check the ports and make sure it's the right port

@Sowens 

Flashing means that data is passing. It's normal. The port with the orange stripe is a 2.5 gigabit capable one. If you plug a 1 gigabit device into it, the light will be orange because a 2.5 gigabit connection has not been established. The other ports are 1 gigabit capable. When you plug a 1 gigabit device into them the light will be green indicating that a 1 gigabit connection has been established.

Green indicates that a full port speed negotiation has been established (whatever the speed capability of the particular port happens be).

Orange indicates that a full port speed negotiation has not been established (whatever the speed capability of the particular port happens to be).