If my machine unexpectedly reboots, my ssh keys no longer work. Initially I would go create new ones and add them to Github and other dev services.
$ ssh-add -l
The agent has no identities.
Bummer.
I didn't need to create new ssh keys, I just needed to add the existing back to the ssh-agent identities.
$ ssh-add -K [path/to/private SSH key]
Mine would look like
$ ssh-add -K .ssh/id_rsa
Nice.
This question answered everything for me. 🙏