OpenAI API keys in free account

I have genertaed openai api keys in the free account. But these keys are not working. I got this error
Screenshot 2023-09-03 112917

If keys does not give a few limits to use, what it is their purpose?

Is there any possiblility to get some free API credits in free account just for testing purpose?

Hi and welcome to the developer forum!

There is no “free account” for API. The use of the service costs money by the amount of data used.

There is only possibility of a free trial credit, which expires three months after you first created your OpenAI account.

Now you’ll need to purchase a credit balance in order to make calls.