iMac Pro will not connect via ethernet at greater than 100m

Just got fiber internet at 1Gig. From the fiber box to my router (Netgear) and to my iMac Pro I am using CAT 5e cables. When I set up the ethernet connection I changed the hardware configuration to 1000 base t. When I look at the system information under about this Mac it shows a 1G connection. Using Speedtest or internet speed test on my iMac Pro I only get speed around 90Mbs. I have connected to my router with the manufacturers software and did a speed test from the router and it show 975 Mbs. My internet supplier shows my connection and my router connecting at the high 900s Mbs. If I disconnect the ethernet and use the built in WiFi on my iMac I get 250 plus Mbs. Why can I not get speeds of 900 or greater on my ethernet connection?

m***********@mac.com

[Edited by Moderator]