Final Fantasy XII help! Stilshrine of Miriam?

Ok, well obviously you've done everything right, and you've equipped the dawn shard correctly otherwise the first pedestal would have caused you a problem. So, what now? Well the pedestal is supposed to open hidden passageways in the neigbouring area to where it stands. Have you run back there and checked to make sure that hasn't happened without you noticing? If it hasn't then I'd try switching party leaders around, try touching it without the shard, then equip it and try again. But be patient, often I found in that game that when what the guide said should happen wouldn't happen, it was mainly due to me being too hasty and expecting the wrong thing.