SUET not being touched

Thrilled to see Red Bellied Woodpecker show up yesterday at tube feeder. Went out and bought a WBU suet cake for him. He's back today at tube feeder, not suet. Up to now suet as been total bust. Do not know why birds won't eat. Tried many brands thinking something wrong. Now WBU suet not being eaten. I bought regular thinking birds not happy with no melt. Any ideas why suet rejected?