Vector Store linked to Assistant - not updating quickly?

I created a vector store, added a file to it and linked it to my assistant. In the playground, I can query the assistant and have it reference the store, giving appropriate answers.

Via the API, it seems that the assistant is unable to reference the new vector store. Is there some lag associated with the API and vector stores that have been recently linked to assistants?

I verified that the assistant id is correct for my API calls (the same as the assistant I used on the playground).