SSH Authentication stopped working

Question

Following the macOS update (to Monterey 12.6.1) my ssh authentication stopped working. I was getting a "Repository not found. Please make sure you have the correct access rights."

I have reset my ssh setup and followed Github's official guidelines on link

My current ~/.ssh/config looks like this:

Host *.github.com
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/id_ed25519

I now get a new error that I haven't been able to solve. When I run ssh -T git@hostname, I get "Bad configuration option: usekeychain"

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I have tried the following fixes:

• Adding to config: IgnoreUnknown UseKeychain
• Adding to config: IgnoreUnknown AddKeysToAgent,UseKeychain (link)
• Clearing DNS cache: sudo killall -HUP mDNSResponder
• Removed ~/.ssh/known_hosts
• Changed hostname to Host *

Answer 1

I had a similar issue to this when I had accidentally written over my public and private key. To overcome and reset this I

1. Deleted all github related ssh keys from the key chain and .ssh/ directory.
2. Deleted github ssh key from github ui.
3. Ran ssh-add -D to remove all identities from the agent.
4. Re-created the ssh key and saved the public key on github.

Obviously this is quite heavy handed!