Hitron E31N2V1 & older routers connectivity issue. - Time Warner Internet

This question is about "Hitron E31N2V1 & older routers connectivity issue.", with Time Warner Cable internet and apps. I have having issues connecting a older Linksys WRT54G router to this Hitron E31N2V1 modem.

When connected I do not get any connectivity. Can't do anything. I have factory reset the router. These routers worked fine with my old fios service. Is this becasue the speed is 400Mps?
If it is simply becasue the router is old, what is a good one that I should replace it with?

The router that Spectrum provided will not let me access a DMZ / port 80 internal address for my video cameras. I hope another router will let me.

Hitron E31N2V1 & older routers connectivity issue.?