@Mark Lui Thanks for reaching out. Apologize for any inconvenience caused on this. I am unable to reproduce this issue at my end could you please try below steps.
Refresh the Azure portal page and try creating the function app and function again or try creating the function app and function using a different browser or device to see if the issue is specific to your current environment.
If the issue persists, you can try creating the function app and function using Azure CLI or Azure PowerShell. This can help you determine if the issue is specific to the Azure portal or if it is a problem with your account permissions.
do let me know incase of further queries, I would be glad to assist you.