Could be any number of reasons. They are a woodland plant but need some sun early season. So if they were on the north side of a building that could be an issue.

They like a moist, rich but well drained soil and appreciate leaf litter like a forest floor would provide.

Too much heat and sun in late spring/summer can stress them and they do not like competition from more aggressive plants. Hope this helps narrow down the problem yours might be having.

Thank you!

Thought I could help seeing as I have thousands of these in my back yard but to many to notice if some dont flower