OP, just to let you know that they might well have tried everything. That they might not be, as other posters have implied, cruel or just plain lazy. I understand how annoying it is for you, and losing sleep is no fun. But I also know what it is like from the other side, as the mother of a toddler who for a long time screamed her way through the night.
DD was a nightmare, frankly. She went from waking every 45 mins as a baby to having massive screaming tantrums pretty much every night as a toddler, sometimes for up to two hours. There was nothing we could do. We tried everything. Sought medical help. Read every book, tried every "regime". Stayed with her. Left her to cry. Put her in our bed. Got her up and distracted her. Fed her. Didn't feed her. Got her a different bed.
Nothing we did helped. We were (are) in a 2-bed house, with our son sharing a room with her. We had nowhere to go. My DH and I almost got divorced, we were so tired and angry. I got post-natal depression. This went on for over 2 years (actually, almost 3).
It wasn't because we were bad parents, though I did for a long time think it was my fault. There was no reason for it, and eventually she just started sleeping normally. When she did, we all got our lives back, though it has taken a long time and a lot of work to salvage the relationship between DH and I, as we said such vile things to each other and argued so much, purely because we were so tired and stressed by it.
I tell you this not as a "poor me", but so that you can see it from the other side. It doesn't diminish how you feel, and they should be apologetic and very sorry for causing you a lack of sleep. I know I was to my neighbours and kept checking in with them, and took them bottles of wine as it went on for so long.
But if I'm very honest, had they knocked on and told me I was keeping them awake... well, it wouldn't have helped. I probably would just have collapsed and cried and cried on them. And it would have added pressure to an already highly pressured situation.
YANBU to speak to them, but tread carefully and be aware that it's unlikely to make much difference. But for all your sakes, I do hope the toddler starts sleeping soon. It's a shit situation all round.