I have the same issue. It creates the connector without code enabled and the moment I enable the code (even with the 'Hello World'', I get the error message.
Failed to provision compute for custom code. Request failed with error 'Code: BadRequest. Message: Unable to find an unassigned function app in 'West US'.'. The correlation Id is '183d5f04-17ec-4193-a5b5-4787c42b4582'.
It seems like a possible license restriction? I thought it was because I had another custom connector open, but same message.
Any further ideas for troubleshooting?