That line may be commented in the config file.
@ -29,7 +29,7 @@ fi
export GPG_TTY="$(tty)"
# Integrate with the SSH module.
if grep 'enable-ssh-support' "$_gpg_agent_conf" &> /dev/null; then
if grep '^enable-ssh-support' "$_gpg_agent_conf" &> /dev/null; then
# Load required functions.
autoload -Uz add-zsh-hook