Is there any more details to the error message received? Any trace of either a "ORA-06512: at "SYS.UTL_HTTP"" or "ORA-24247: network access denied by access control list (ACL)" in the logs?
My guess here would be that the ACL - or database Access Control List - has not been configured to allow APEX to call an external web service.
- Scott -
Thanks for taking the time to reply. It seems it was an ACL issue - just didn't seem to be showing up in the error messages.