If you’re using the en_core_web_sm model, that warning is expected, because that model doesn’t have any word vectors. For all other models, it usually means that one or more seed terms you’re trying to add are not in your vectors table. However, it does seem unlikely given the terms “great” and “excellent”.
What do the suggestions look like when you use a model like en_vectors_web_lg and you go through them in the app? Do they make sense?
Edit: Okay, I can reproduce this with the large vector model. It seems like for some reason, spaCy thinks that the underlying lexemes it’s comparing (seed terms vs. model vocab) do not have vectors. So the similarity comparison doesn’t produce any results, and the user warning is shown (which is really just a warning, because spaCy does allow empty similarity comparisons – it’s just normally not what you want and a very helpful warning in cases like this).