I'm an anemone guy. I can grow and have success with just about all of them: BTA, RBTA, rock anemones, tube anemones, you name it. I've bitten the bait and twice bought gorgeous LTAs from the Dome only to have them wander in my tank, not attach, and ultimately die. I've tried just about everything. The reason I say this is that LTAs can obviously be difficult.
I finally settled on the idea that they don't like the other anemones in my tank. I've researched and read numerous articles that say that LTAs don't like tanks with BTAs in them (despite seeing the massive tank at the dome that has nems of all types in it). So, what other livestock do you have in the tank?
Try the things listed above, see if you can find somewhere for it to settle. The closest I came to success was when I provided a 4" piece of pvc with live rock rubble and sand in the bottom. One of the LTAs stayed in it for almost 10 days, opening to feed, before it ballooned up and started drifting all over the tank.
Best of luck, and let us know if you figure it out.