Dave lives in a town that was recently effective by the wildfires and he discovered that everything from his internet access to his phone service was disabled. Leo says that's because Dave's location uses fiber optic cable and as such, when firefighters cut the cable while fighting the fire, it disabled EVERYTHING.
Dave is also trying to back up his data using Time Machine and his backup was lost. Leo's not crazy with Time Machine. He suggests reformating your backup disc and Time Machine will automatically ask you if you want to use it for backup and run it right there. You won't get the old backup back, but you can at least reset it moving forward. macOS Big Sur is going to change the game though, by changing the file system to APFS, which will allow for snapshots. Once that's done, Time Machine will be more reliable.
But there's a better option: the Super Duper from Shirt Pocket. And what it will do is make your backup drive bootable.