Don't worry, its growing up as well, just not nearly as fast as it grows out.
Most will encrust, in a razor thin sheet across the plug. Then devote its energy to thickening up that razor thin sheet to stabilize the coral, then developing polyps, then extending branches.
SPS grow fastest when you aren't watching and you don't care lol. If your watching for growth, you'll never see it.
Unless you set your camera up on a tripod and don't move it, take a photo on the same settings, in the same spot, without moving the camera each day at around the same time for a week or better, a month. Compare the photo's "¦ you'll notice growth, just not too much haha
If you want speed. Seriatoporas and Pocciliporas will be the way to go. I have an ORA Nuclear Green Birdsnest that I am pretty sure I can see growing if I stare hard enough lol