just be patient. as long as its attached through the substrate you should have an idea of how its doing. mine didnt eat for a week either.. it would grab the food then immediately let it go. you also need to offer it very small pieces, and i mean small. my guy is only 4-5" across, but i have to feed it pieces smaller than an eraser end, otherwise it wont eat it.
also, try offering it raw shrimp that you find in your grocery seafood section. i find that mine loves eating raw shrimp. just take it out of the freezer, cut a small piece off, rinse it in saltwater and let it defrost, then get a turkey baster and gently blow it into the tentacles of the LTA