It's easy to hit OpenAI API's rate limit if you're using their 'Free Tier' or 'Tier 1', as they have imposed a daily request limit for these two tiers.

It's recommended to upgrade your plan to at least 'Tier 2', which does not have a 'request per day' limit. As of today (April 26, 2024), you can simply top up $50 in your OpenAI account and wait 7 days to be automatically upgraded to Tier 2.

Reference Link: Rate limits - OpenAI API