1 Gig speed limited to 100Mbps on Mac mini

I have a 2014 Mac mini capable of 1 GiG internet speeds. I have Verizon fios 400/400 and have verified speed is higher than 100 via other devices. I see my MAC is set to 100 and when I change it to manual and 1000base t it tells me the Ethernet is no longer connected. If I switch it back to auto it works again and defaults back to 100. All of the speed tests I do come out in the nineties so it is limiting it to 100 or less. I chatted with Verizon and they said I needed to contact Apple. I feel like perhaps some of the other settings need to be changed to allow the computer to speak to the router and allow the speeds of greater than 100 Mbps. Another poster had the same issue but there is no resolution to his post. I have checked the cable, I am on Ethernet, and I have checked my speed with other devices and it is currently running around 270 Mbps. Perhaps the Duplex or MTU settings need to be modified? Thank you for the help.