github "Repository not found fatal: Could not read from remote repository" error, troubleshooting and fix

Yesterday I'm suddenly unable to access repos I work with on a daily basis. When I rebase or try to clone I get this error

ERROR: Repository not found.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

Nothing changed. My github credentials un-chanaged. My ssh keys unchanged.

I was able to fix by regenerating my ssh keys but read on for tips on troubleshooting

• there's a good troubleshooting page on github with help on common issues
• first, test your ssh connection and identity using `ssh -vT git@github.com`
• see more here
• when I ran this command I noticed it's response "Hi <id>, .." was not the id I expected and clearly a problem
• 
  
• check your `~/.gitconfig` (does it looks correct?)
• check the email and userid used in your repo, they should be as expected and be associated with the ssh key locally and also in github
• you can unset 

• git config --global --unset user.name
  git config --global --unset user.email
  git config --global --unset credential.helper

In my case I don't know why this problem started, but the fix was to regenerate my ssh keys AND edit my `~/.ssh/config` file IdentityFile property value which was wrong (no longer matched the latest ssh key generation steps). Need to be: `IdentityFile ~/.ssh/id_ed25519` 

Then add the ssh key to github

Then when I re-ran `ssh -vT git@github.com` it was correct. Pain in the butt problem solved.