The code snippet says “res.status” and not “run.status”, not sure if that’s a typo. But the symptoms you describe sound like you’re retrieving the messages before the run has actually completed.
This is discussed in the related question Retriever Assistant API not giving answer but playground gives
I’d suggest copying their polling code. Also at the same time you’re displaying the messages, print(run) and look at resulting parameters like created_at, completed_at, status, thread_id, etc. for more clues.