Rate limit error

Although it seems that I still have some usage for OpenAI API, I'm still getting RetryError: RetryError[<Future at 0x7f80f93c0a60 state=finished raised RateLimitError>] when I try to run the codes on https://gpt-index.readthedocs.io/en/latest/end_to_end_tutorials/chatbots/building_a_chatbot.html . Do you have an idea why I'm still getting this error and what I can do?