The coraline will come. Keep the calcium, magnesium, and alkalinity up. If you really wanted to, you could add a product such as purple up. But really, it just takes time and decent parameters.
I have had my tank up for 6 months and I am just now getting coraline to grow on my glass like shaunv said it just takes time . I was told of you put in some big chunks of live rock covered in coraline it can help speed it up a little but not much
[h=1]Brightwell Aquatics BoroChrom - Concentrated Boron Solution for Coralline Growth & Red Coloration I use this I add when I do my water changes it builds up on the glass fast so have a scraper ready[/h]