I took the elevator up to kerah, listened to her talk... BUT I went back down before using the portal of Isis, or getting the light toy from Kerah (or doing anything related to leprachans). Now I can't get back up. Do I have to restore, or is there something else I can do to get the light reflected from the pedestal to the ashes on the altar? I really don't want to restore, because I saved after coming back down, so... restoring would mean losing all I have done in the shrine till here. Please advise. Thanks.

Have you tried picking up the small statue from the altar and then putting it back on it?

Yeah. I tried that. The narrator gives his spiel again, but the stone slab stays stuck in the up position.