No internet/modem says no signal

My internet was working fine all day and suddenly dropped out, after going through 100 checks of my cables tight and plugged in I talked to someone who said my modem isn't receiving a signal, after going back and forth they did something with a boot file which seemed to fix it and then said docsis health is red and my internet went out again. I haven't had any issues and no reported outages before this.

Why suddenly can my modem not be found/signal and no internet?