I got one from an LFS
recently that they were "training" to open at a decent early hour. Basically tempting it with food every other day at 6PM.
So I'm doing the same and got the first real response yesterday. About 4 days after bringing it home actually.
Cut the top off a plastic bottle (check YouTube) and cover it while feeding. Stop water movement. This just keeps the food where you want it long enough for it to respond & open up. It took ours about 40 minutes last night, then we used puffs of water from the feeder tube to stir up the chunks in the bottle cover again. It took a while but was fun to see it finally respond. I don't think we got all of them fed but we'll get there.