training it with food at the same time everday sometimes for 2 weeks +- is a proven method. they are fickle until you get them trained. religious dedication, but worth it if you ca get them to eat. if you do not see them open at the store or if the LFS cannot entice the feeders out, they are often in a state of starvation and duress.=== plump polyps are good, sunken in, withdrawn polyps are not. think of a closed polyp like a skinny or fat polyp....fat polyps good, skinny polyps not as much.
and of course, that does not go to say that they can not be saved or nourished back, but once they have withdrawn, they are far more difficult to coax into eating again.