The issue and resolution are discussed here.
You need to change your @hydra.main definition to have config_path='embeddings_and_difficulty/configs_hydra', and note the interface differences in the guild.yml between your train definition and what we’ve put under train-2 here.
Additionally, as a hydra user you may be interested in this RFC: Value dependent flag definitions/flag groups - RFC - Guild AI which should enhance your ability to work with more complex hydra structures.
Let us know if this fixes your issue, or if it still persists.