Can anyone tell me why my day lilies have not flowered the last couple of years?

Try and treat them with fertilizer for flowering plants. Might they need some boost. The day lilies I have are just starting to come out yet. But some that are in the shade are not doing great. If you're in the same area as I am, maybe they're not out yet. Wait a little and for the meantime give them a shot of flowering fertilizer hoping they'll come out.