Wireless router not able to connect to internet through Xfinity modem

I recently purchased a TP-Link AXE5400 wireless router to take over managing my home's wireless network from my rented xfinity modem (model XB7-CM). I enabled bridge mode on the modem and followed the simple steps provided by the wireless router to set up a new wireless network. However, while everything else set up easily, right from the start the new router showed an error light for internet connection, despite being connected to the modem via an ethernet cable (I tested, both the port and the cable worked fine to connect my PC to the modem). I went through all the troubleshooting steps provided by the router (including doing a factory reset on the router and setting it up again from scratch) but no internet connection. I restarted both the router and modem multiple times and even tried resetting the modem's MAC Binding by unplugging the coaxial cable for five minutes. Nothing worked. I tried using the xfinity virtual assistant but as always it was no help. The best it could do was schedule me an appointment with a technician four days from now. 

Hopefully someone here can provide additional fixes I have yet to try. Thank you for your assistance.