If it is a Zantedeschia they often don't bloom unless the conditions are right. They do need good rich compost to do well but also warmth and sufficient water in the growing season. In our climate they will only do well if we have a good summer and get a head start in a greenhouse, otherwise they struggle, we have a lot of cool summers and cold springs.
Yes I would leave it to die back, then you could lift the bulb or corm and take photos of it to post here then we might be able to give a better idea. A fresh Zantedeschia corm will be a dirty whitish colour with a loose skin, if it's allowed to dry it becomes wrinkly. They usually make more corms with some detached, some small ones still attached.
