Slow Upload speed

I have an Xfinity Wifi Gateway.   After switching from a 500Mbps internet plan to the 2000Mbps internet plan, my upload speed dropped to 1.5 Mbps.   I am using the Xfinity Wifi Gateway in "bridge mode" and it is connected to a TP-Link AX1800 Router.    The slow upload is only applicable to my hard wired ethernet connection.  My wi-fi connections are fine.

I did not have this issue prior to changing my plan from 500Mbps to 2000Mbps.   I have changed out the modem and the router hardware AND still have the same issue.

I have researched the heck out of this and determined that most likely problem is I do not have the correct "boot file".  How can I get Xfinity support to Update my Boot File?