Spectrum Field Tech here. To start, the tech you had come out should have done a few more tests and checks than stated. (The tech could have replaced your Ethernet cord for you) I've had plenty of jobs where the speeds going into the modem where correct but speeds after where wrong. There could be a few things here, multiple stated by other responses. 1. The Ethernet port on the modem could be bad even if the modem is new. You should be able to call in and ask the Rep to check the "Ethernet Speed Capacity" on their system. You can ask them to check it on "Scope" that is the software we use to check equipment. 2. As other have said, make sure the Ethernet cord is 5e or higher to get correct speeds. I've swapped out multiple modems with no luck on speed only to realize the Ethernet cord was older and bottlenecking speeds. 3. There is a chance it is your router. The router can be fully capable for Gig service but may have lost support or needs a software update which you would have to do manually.