Custom tree feature does NOT spawn whatever I do

I don't know if I should put that in bugs, I honestly have no idea. I have made a mod less than a year ago with custom tree features (with custom structure files) , and it worked well, then I copied it into another mod that I wanted to add custom trees to, I even copied the same conditions, but for some reason, it appears not to work. They just don't spawn at all in the designated biome. Whatever I try, it just doesn't work. I have a lot of other features generating in that biome, and they work, but the trees don't want to generate for some reason.