The English is "I see you in person at last and not just on a photo."...
Is there anything wrong with my translation "Ich sehe dich endlich in Person und nicht nur auf einem Foto"?
It's fine. By the way, "Photo" is an obsolete spelling of "Foto". The English sentence seems a bit dodgy as well.
the more natural preposition in English would be IN rather than on. someone is seen ON television, IN a film, and in a photograph (and heard ON the radio.)
I don't really like the 'in Person' here and would vote for 'Endlich sehe ich dich mal persönlich'. But that's just a matter of taste.