After editing the config and adding cobbled_deepslate I get the following errors:

[15:40:46] [Worker-Main-9/WARN] [minecraft/ModelBakery]: Exception loading blockstate definition: 'compressium:blockstates/cobbled_deepslate_1.json' missing model for variant: 'compressium:cobbled_deepslate_1#'
[15:40:48] [Worker-Main-9/WARN] [minecraft/ModelBakery]: Unable to load model: 'compressium:cobbled_deepslate_1#inventory' referenced from: compressium:cobbled_deepslate_1#inventory: java.io.FileNotFoundException: compressium:models/item/cobbled_deepslate_1.json

and so on for every level of configured compression. Obviously cobbled deepstone does not compress in game, as a result.

Thanks

Edit:
Forge version: 41.0.38
mod version: 2.1.0 build 7

see issue #7. Also please use the issue template next time