Training neuralcoref for my own custom entities

I have a corpus which is in CONLL format for my own list of entity classes. I trained my own custom ner model for this corpus successfully going through spacy.

Now I want to try to train a custom neuralcoref model using this same corpus. I try to start at he `python -m neuralcoref.train.conllparser` step on my conll files, but I get an empty key.txt file and an empty numpy directory as a result. Is there something that I am missing?