Purple up is basically a calcium additive to promote the growth of coralline. It does not contain any strains of coralline, so that will still have to be introduced to your tank via rock, frag pug, shell etc in order for it to actually grow.
I would keep an eye on calcium levels and when adding purple up. Aiming around 380-420ppm is a good range. If you want to promote coralline, maintain Alk and Mag levels within range also. That along with decent lighting, and eventually, it will grow.
Btw, I do not find the test strips to be accurate at all, I would suggest salifert or Hanna for Alk, API or salifert for Calcium, and Salifert or Red Sea for Mg.