GitHub deploy key verification failure and unable to generate new key

After last week’s break-in, I started seeing “public_key.verification_failure” errors in the security log for my linked GitHub account. I figured I had to create new public keys for my automatic builds so I went to the automatic builds settings for one of my repos, and clicked “Generate” under “Deploy Key”. This resulted in the generate button getting grayed out but nothing else actually happened: no deploy key was added to the repo, and there was no new key signature in the text box below the button. Can someone help?

Thanks,
-Mat