"Ça ne va pas de soi"
Rien d'autre ne me vient à l'esprit comme ça sans plus de contexte...
I am afraid it wouldn't work.Supposing the context was:
Person 'A', who appears to be in their thirties, informs Person 'B' that they are in fact 50 years old.
Would it make sense for Person 'B' to reply "Ça ne parait pas!" as a way of expressing a kind of surprise and to basically say "wow you don't look 50!" ?
Or ça ne se voit pas, depending on the context, I think.