Ethernet not working in bridge mode

I have a Xfinity 6 gateway.   When I plug my laptop into the gateway via ethernet, I have connectivity (WiFi turned off.)  In bridge mode, there is no ethernet connectivity when my laptop is directly plugged in (regardless of left or right ethernet port.)  I discovered this issue after my Orbi Router went down after a few months and I have been unable to re-connect as it keeps saying there is not internet.  Any thoughts on how to fix?