[FL] Slow net forced use Mediacom modem, won't work with ethernet switch

I recently upgraded my Mediacom Internet Service to Ultra and got a new modem (technicolor Xtream) with phone service (mainly to reduce the bill I had with the lower speed service). I had the modem baselined so I could use my router. With my Linksys WRT1900AC router, I tested my speed today. I was getting around 20mbps. I called Mediacom. They asked me to try connecting the Mediacom modem directly to my PC (A Mac Mini late-2014 running OS X 10.11.3 El Capitan). I got 100mbps or more. I didn’t want to pay monthly for WiFi, so I tried another router, an Apple Airport Extreme 6th Generation (current model). I got around 60mbps. I called Mediacom again. I had the Mediacom modem taken off baseline. I decided a $2 charge, plus $3.95 a month was necessary. The WiFi works fine, but I have an ethernet problem. I plugged my Netgear ProSafe 8 Port Gigabit Ethernet Switch (GS108) back into the Mediacom modem. I then had no ethernet connection to the internet. I tried connecting my PC directly to modem port 1, and the switch to port 2, but no ethernet internet connection. I need to be able to use a switch for multiple non-wifi devices. I was tired of the phone calls, so I tried the Mediacom chat. The connection died while the technician seem to still be trying to get a grasp on the nature of the problem. I didn’t receive a return call. I switched my plan to save money. I would prefer to I recently upgraded my Mediacom Internet Service to Ultra and got a new modem (technicolor Xtream) with phone service (mainly to reduce the bill I had with the lower speed service). I had the modem baselined so I could use my router. With my Linksys WRT1900AC router, I tested my speed today. I was getting around 20mbps. I called Mediacom. They asked me to try connecting the Mediacom modem directly to my PC (A Mac Mini late-2014 running OS X 10.11.3 El Capitan). I got 100mbps or more. I didn’t want to pay monthly for WiFi, so I tried another router, an Apple Airport Extreme 6th Generation (current model). I got around 60mbps. I called Mediacom again. I had the Mediacom modem taken off baseline. I decided a $2 charge, plus $3.95 a month was necessary. The WiFi works fine, but I have an ethernet problem. I plugged my Netgear ProSafe 8 Port Gigabit Ethernet Switch (GS108) back into the Mediacom modem. I then had no ethernet connection to the internet. I tried connecting my PC directly to modem port 1, and the switch to port 2, but no ethernet internet connection. I need to be able to use a switch for multiple non-wifi devices. I was tired of the phone calls, so I tried the Mediacom chat. The connection died while the technician seem to still be trying to get a grasp on the nature of the problem. I didn’t receive a return call. I switched my plan to save money. I would prefer to save the monthly WiFi fee and use my own router, which has better WiFi range. However, I’m willing to pay it if everything works and I get the promised speed. I need a solution that works with my home network, including the ethernet switch.