I candled my eggs on day 18 and seen movement in most of them. None of them ever hatched. In your experience, what would be the most likely reason why all of them died in the shell. Temperature seemed to be right on, and so did humidity.
There are a number of things that can cause this. Unfortunately most people will never know exactly what it was.
There have just recently been a couple people suggest air flow as a culpret. I suspect that was the issue for me when I had a very large batch going. The eggs need as much fresh air as the living chicks will need in the last 3 days. If there is not enough fresh air....
There could also be temp spikes & drops that cause it or hot / cold spots in the bator.
or genetic issues with the chicks themselves - I've read that aracauna's can carry a genetic defect that makes them difficult to hatch.
If the temp & humidity were correct - I would look at air flow first - after ruling that out - hard to say.
I just completed a very successful hatch ( of the 50 that went into lockdown only 6 didn't make it). The 2 hatches I had before this one all my chicks died in the shell. The reason being: not enough air flow, too high humidity and too many temp spikes. This time I kept my temps between 100.9 and 102.3 and I didn't add water during the first 18 days. I filled up both water troughs in my incubator and added 2 wash clothes and kept my humidity between 50-60% during lockdown. It spiked up to 70% a few times after the chicks started hatching. These temps and humidity may not work for everyone but for me it was a very good hatch rate. I have 3 little giant still air incubators with no turners.
ChooksChick has a really good cheat sheet on her profile which really helped improve my hatches.