Comcast.
As I mentioned, for some odd reason I had to put in the old MAC address to get the new router to work. It didn't fully work btw, this only allowed Ethernet connectivity.
I think what you experienced is a coincidence. Remember I said I waited it out and connectivity was restored? I did no additional power cycling, no configuration changing. After I logged in to confirm the router had no internet connection through the modem I simply logged out and waited. Shortly afterwards, I had internet connectivity.
I think the problem is the router because cable modem or not, the signal it gives off is completely inadequate even when I a, in the sa,e room. I'm talking like going from two bars five feet away to one bar ten feet away. It should of course be full bars twenty feet away.
You're exactly right it is the router. You had two things happening at the same time and you are trying to conflate them. They are not related, one is the consequence of putting a new router into the mix (because of which you ended up cloning the MAC) the other is a problem router (poor wireless).
I believe that if you had strong wireless signals out of the box that you still would not have had internet connectivity until a short period of time had passed. In my case it was probably two to three minutes. Yes, that's an eternity in today's world and especially in one where we are programmed that if we power up the modem and wait until the lights are stabilized and then power up the router and wait for the lights to stabilize that we will have the connectivity we expect.
Comcast is doing something different these days. I cannot say what. But I do know that the modem, once installed is their territory and they control the configuration, the "flash". I think that they changed something in regards to how it deals with the MAC of the device connected to the modem. It may be just that they only poll for a change every few minutes instead of doing it much more frequently. Once again, I don't know but I do believe something has changed.
How Comcast operates in Michigan versus how they operate at my second home in Florida is totally different but that is another story and one that will just cloud the issue.
Once again, try a reset and then a flash if it's not fixed before moving on to the next step. I think you may not necessarily have a "bad" router, just a "confused" router.