NET::ERR_CERT_AUTHORITY_INVALID on email

We installed this modem/router on May 21st and it was working fine.  About a week later we started getting errors when trying to access gmail through various browsers and when trying to play multiplayer games on the xbox.  I searched the community and one of the suggested solutions is that the date and time on the router needs to match the computer.  I can see on the routerlogin.net that the time on the router appears to be Pacific time and therefore is one hour behind the computer.  I can't figure out how to correct the time on the router.  Have tried unplugging and restarting without any correction.  I can't show the event log because I can't access any of my email sites (comcast or gmail) when I'm hooked up to the home network.  My computer works fine when connected through my work VPN.  

The log shows erros like SYNC TIming Synchronization failure and Unicast Maintenance Ranging - No response recieved - T3 time-out, No ranging response recieved.  WIFI interface set to Channel 3, Honoring MDD; I provisioning mode = IPv6 and Dynamic Range Window violation.  Dates range from 5-24-17 to 6-13-2017 with some 1970-1-1 dates in-between.

Any thoughts on how to fix?