From what I’ve seen on the forums the DNS issue is with eero wifi systems. There are a couple of threads on the topic, but this one suggests a workaround has been implemented in Plex in the interrim though the real problem needs to be fixed in the eero firmware.
A good place to start would be to look at your Plex Server logs, preferably at debug level. The automatic guide refresh is supposed to happen nightly, initiated by the butler during the window you have set in Plex Web under Settings → Scheduled Tasks. If you have given the butler a small window to run it could be a problem. If you look in the logs (the logs roll, so “Plex Media Server.log”, “Plex Media Server.1.log”, etc.) starting at your set schedule start time you should see where the butler schedules the EPG refresh with a line something like “Butler: Scheduling randomized task ‘RefreshEpgGuides’ in 237 minutes.”. Figure out when this would be and go to that time in the logs and look for EPG guide refresh activity starting, such as “Activity: registered new activity xxxxxx-xxxxxxx-xxxx-xxxxx - Refreshing guide data” (and look for errors.)
Also in Plex Web go to Settings → Manage → Live TV & DVR, and click on “DVR Settings”. Scroll to the bottom of the window that pops up and make sure “Perform Refresh of Guide Data” is checked. Just under the “DVR Settings” link is a “Refresh Guide” link where you can manually initiate a refresh, which can be helpful while troubleshooting if that successfully works, or if it fails you can note the time and then the EPG refresh error will be near the end of the “Plex Media Server.log” file if you go and download logs a couple minutes after the error.
