azd provision Azure Function App InternalServerError

[mmurray-engineer]

I'm creating an Azure Function using this quickstart:
https://learn.microsoft.com/en-us/azure/azure-functions/create-first-function-azure-developer-cli?pivots=programming-language-csharp&tabs=linux%2Cget%2Cbash%2Cpowershell

The function runs locally.
I'm using Visual Studio Code.
However, when I try to deploy to Azure, I get an error for the provision step.

InternalServerError: There was an unexpected InternalServerError. Please try again later.

I have tried this over a few days, so the error is not transient.

Most resources are created, but the error occurs for the Web App: func

The Azure portal shows the deployment details and includes 'Status = BadRequest' but the error details only mention the internal server error - there are no further details.

All bicep files are valid according to bicep linter.
I have compared files to other azd templates and the key file, functions-flexconsumption.bicep is the same.

I have tried azd down to clean up resources, then try again with azd provision but the same error occurs.

The --debug flag provides lots of details, but not enough to identify the problem.

How can I discover the cause of the error?

Thanks