WARNING: No source added in .add_source_document

I followed the following LLMWare tutorial on YouTube and ran into the following error when using Prompter.add_source_document().

source = prompter.add_source_document(contracts_path, contract, query=key)

This gives me a Warning that the source was not added.

What could be the issue?

My contracts_path = ./docs/. My files do have spaces in their names, but I doubt that would be an issue. Could it be the file-type suffix?

Tutorial Video Followed: https://www.youtube.com/watch?v=8aV5p3tErP0