Slow ethernet upload speeds

Wired connection is currently stuck at <5mbps on a cat8 cable. Current plan advertises up to 300mbps upload speeds, and I would like to get up to at least an acceptable level. To the best of my knowledge, it's not a device issue as it is happening on both a desktop PC and console, and I don't believe it can be due to any device settings for the PC. Using an XB6 gateway and have tried both ethernet ports to equally disappointing results. The Wi-Fi speeds are fine, sometimes as high as 100mbps upload, but I really need to get the LAN speeds up to where they should be. Any assistance would be appreciated.