Hello Thomas Lowrey,
Welcome to the Microsoft Q&A and thank you for posting your questions here.
I understand that you are having issue with connecting your Copilot to Azure OpenAI Services for accessing your data index.
I will advise you to enable CORS for your Azure Blob Storage resource if you are using it to store your data, this is a similar situation here https://learn.microsoft.com/en-us/answers/questions/1513627/problems-integrating-azure-openai-in-copilot-studi but if the issues is not resolved, refer to these documentations https://learn.microsoft.com/en-us/azure/ai-services/openai/concepts/use-your-data and https://learn.microsoft.com/en-us/microsoft-copilot-studio/nlu-generative-answers-azure-openai
I hope this is helpful! Do not hesitate to let me know if you have any other questions.
Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful.