@Suyeol Yun Welcome to Microsoft Q&A Forum, Thank you for posting your query here!
Plan 1:
Firstly confirm if you have the Cognitive Services OpenAI Contributor
RBAC permissions on the resource.
Plan 2:
The Azure OpenAI Service quotas and limits are explained in details here. Please ensure that the quota limit is not exceeded. You can check your current usage by following the below steps:
Open the Azure AI Studio from **this link. **and select the concerned subscription and resource.
For an all up view of your quota allocations across deployments in a given region, select Management > Quota in Azure AI Studio:
More info here.
If you are reaching the limits, click on the Request Quota
link on the right side.
Hope this helps. If you have any follow-up questions, please let me know. I would be happy to help.