PSA: If you have a Eufy security system with a Eufy HomeBase 3 and all your cameras (eufyCam 3 S330, Doorbell, etc.) go offline after a HomeBase reboot (power outage or manual), I finally fixed it after much troubleshooting and wanted to share the solution.
Note that the HomeBase showed a solid blue LED (internet connected), but the cameras would never come back online. Another oddity was that my Indoor 4K (wireless) cameras didn't have this issue, they came back OK - only the eufyCam 3 S330 and Doorbell failed.
The fix: change the HomeBase DNS server to a different one (e.g., Google 8.8.8.8 or Cloudflare 1.1.1.1).
You can't make this change from the HomeBase interface (that I can see anyway), but you can do this from a router level (i.e. set a static IP and manually configure it's DNS server.)
I had a network-wide family-protected DNS active, which was somehow preventing the cameras from reconnecting to the HomeBase after reboot.
Hope this helps someone.
