The solution might've been hiding in plain sight the entire time ...

Two days ago my cable modem/internet connection stopped working, it worked for months before This is the setup. Cable from the wall goes to a splitter, which splits it to one cable to the cable modem ...

I've have cable modem service for over a year now. I've never had problems before recently. Several changes have happened to my setup, so it's hard to pinpoint where the problem is coming from.

Nobody thinks to check the cable that's been working fine for a decade.