It takes time. If you had to re-cure the lr after shipping it may take a lot longer for things to grow on it. What I would suggest is going to your LFS and inspecting some smaller pieces of lr, select one that's got good growth and add it to your tank. Eventually you'll re-seed the rest of your lr with growth from the addition.
It took my lr a while, but once the purple algae took hold the growth of everything (not just algae) was amazing. Like everything in this hobby, it takes time.