Slow upload speed even after requesting an Xfinity gateway for symmetric speeds

Hello. I've recently changed internet plan to a 1Gbps download and upload speed. Download speed is fine, however my upload speed kept to around 30-45Mbps only. I realized my own Arris modem was listed in your compatible device list as only supporting 35Mbps upload limit and the broadband label for my plan states that an Xfinity Gateway is required to reach the typical symmetric speeds. I have requested for the gateway since it came free with the plan. It arrived (an XB8) and i have had it installed and setup for a few days now but my upload speeds is still only around 30-75+ Mbps. Does something else need to happen on your end for the upload speed to reach what it's supposed to be?