As a security precaution, GitHub automatically deletes SSH keys that haven't been used in a year.
GitHub automatically deletes inactive SSH keys to help keep accounts safe, such as after someone leaves a job or loses a computer.
You can check if you haven't used an SSH key in a year by reviewing your account's security log in your GitHub account.
After your inactive SSH key is deleted, you'll need to copy the key from your Deploy HQ project into the corresponding GitHub repository. For more information, see this guide.
You'll also be able to find out more about the security feature in GitHub's documentation.