Gigabit plan but very slow download speeds with direct modem connection

Hi, 

I have a gigabit Xfinity internet plan and use my own modem, a NETGEAR Nighthawk CM2050V.

When my Windows laptop is connected directly to the modem by Ethernet, Windows shows a 1000/1000 Mbps link speed. However, Ookla Speedtest is showing only about 20-40 Mbps download and around 40 Mbps upload, with ping around 10 ms.

I have tried rebooting the modem and testing again with a direct Ethernet connection, but the download speed is still far below what I would expect from a gigabit plan.

Could someone from Xfinity please help check whether my modem is provisioned correctly for my plan and whether the signal levels look normal?

Thank you!