SSH a headache when trying to test connection on GITHUB

Hi community! Today when I was working on GitHub for testing my ssh connection through
ssh -T [e-mail] I got to this error of display in the terminal i.e.

[e-mail]: Permission denied (publickey).

When I tried to find out what the exact reason of this error, as when I have already configured my username and email using the
git config --global user.name
&

git config --global user.email
so why it's showing this error, do anyone have any idea about this?