How does he know the Port is bad?

In addition to the valid question above, I would call Sonos Support directly to discuss it. I don’t think Sonos warranty lasts that long, but it certainly wouldn’t be the norm for them to fail in 18 months. But Support may be able to help you. 

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

My installer took tested and then removed the port to test further at his shop. I do not know what can fail in a Sonos Port. And, thank you, I will call phone support.

Sorry "My installer tested and ...."

Don’t count on Mother Nature to be fair. A given unit can fail at any time. My PORT has been working fine since the model was first released — as are even older SONOS models. We don’t yet know the life expectancy of PORT. There are some older units, such as the BRIDGE and handheld controllers that are thoroughly obsolete and are reaching physical end of life. I cannot give percentages, but the original ZP100 from 2005 seems viable (of course, with a few failures along the way). BTW I found a ZP100 and its successor the ZP120 in a basement yesterday and both are operational.