C7000v2 suddenly won't connect

Has a power off for 1 minute then back ON with the modem  been performed since last update?
Be sure to restart your network in this sequence:
Turn off and unplug modem.
Turn off router and computers.
Plug in and turn on modem. Wait 2 minutes for it to connect.
Turn on the router and wait 2 minutes for it to connect.
Turn on computers and rest of network.

 

Please post a copy and paste of the modems connection status and event log page.
https://kb.netgear.com/30007/How-do-I-obtain-the-cable-connection-information-from-a-NETGEAR-cable-modem-modem-router
https://kb.netgear.com/30008/How-do-I-view-or-clear-the-event-logs-on-my-NETGEAR-cable-modem-or-modem-router

Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended. 

Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Start with removing any amplifiers, signal attenuators, or splitters from the coax.
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, loose connections, bad/old/cheap connectors, or corroded connections. Replace them if you do.
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Modems/m-p/1530376#M12853
https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router
https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html