How to add a feature to a biome file?

I am working on getting Osmium Ore from mekanism to generate on the moon from Ad Astra. Unfortunately, nothing generates. I have narrowed the problem down to my biome file. Any time I add anything (including vanilla features) to the biome file that isn't already in the biome file, I get "datapacks cannot be validated". Anyone know what I could be doing wrong?