Azure OpenAI API key validating but getting 'Bad User API Key'

Attempting to use o4-mini with Azure OpenAI key / endpoint. Dev tools show the API key is validating and the model is responding. However when I try to send a test message in Composer:
'[composer] Error in AI response: {“error”:“ERROR_BAD_USER_API_KEY”,“details”:{“title”:“Bad User API key”,“detail”:“Unauthorized User API key”,“isRetryable”:false},“isExpected”:true} ConnectError: [unauthenticated] Error

Unfortunately we can’t offer much support for Azure deployments, or any API key use, as it’s kinda of offered “as is”, due to the massive complexity it would cause if we offered support for it.

I’ll log this down for the team to look at though, as if this is an easy fix on our end, we’d love to do it!