If using git signed commits a GPG needs generating and associating to the Git workflows.
gpg --full-generate-key
GitHub has some great docs on this setup.
# get key id
gpg --list-secret-keys --keyid-format=long
The GPG_TTY setting is needed to enable the prompt for the private key secret passphrase. (reading reference)
export GPG_TTY=$(tty)'
View the Git README.md with regards to associating the created key.