Talk to Dermatologist on Pico Laser For Dark Lips Not Affective?

I did two sessions of Pico Laser (they put carbon like paste before) to lighten my dark lips, I don't smoke, they were induced by sun damage (but it has been more than a decade since they turned dark and never reversed). Sessions were 30 days apart and just recently did second session.

I see zero lightening of the darkening, its feeling like a waste of time my questions are: 1) how long it takes to see results? 2) how many sessions do I need? 3) Are there people on whom the laser lip lightening does not work?