Could you share more details about the API request you're making? Specifically, what is the size of the payload you're sending?
Can you try accessing the API from a different network or device to confirm that the issue is not related to the network or device?
I suggest you, check Interacting with the model for Use the following practices for best results when chatting with the model.
Also, Consider setting the following parameters even if they are optional for using the API.
Please note that content filtering and abuse monitoring features of Azure OpenAI still apply to the data.
See similar thread which addressed the same issue here : https://learn.microsoft.com/en-us/answers/questions/1276363/problem-with-streaming-chat-api
Hope this helps. Do let us know if that helps or have any further queries,