Slow speeds on Motorola MB8600

I decided to upgrade to a Motorola MB8600 DOCSIS 3.1. It is registered with xfinity. I have the 200mbps down and 10mbps up service but I consistently get 30 mbps down. This is when connected to wifi and when connected directly to the cable modem. I know that the MB8600 does not have its own wifi. I connect directly with a thunderbolt 3 to Ethernet adapter. I tried with my phone and another laptop. Same slow speed. I talked to a tech with the xfinity chat service and he could not see why my internet was slow. I am using the 1 foot Ethernet cable included with the MB8600. I have a tech physically coming to my house on Monday . It would be cool if I could figure this out before then so I don’t have to miss work. Any ideas? Thanks