No Improvement After One Profractional Treatment for Acne Scarring, Will The Others Work?

I had 1 Pro Fractional Laser about 3 month ago for acne scarring. I have med-deep scarring on my cheeks. The procedure and recovery all went well, but there does not appear to be any noticeable improvement to the scarring, in additional there are some track marks on my skin left by the laser. Three month later mostly of the track mark have disappeared but my skin hasn't improved. The derm suggest that I need at least 3 treatments. I'm not sure if I should go back consider the little improvement.