What version your running ? Can you check the log files and post here..
Are you checking at the right composites, there could be multiple composites with different version and only one will be default.
So check accodingly.
It is very good practice mentioning of Jdev version which you are using..
When it comes to your issue. Please mention the way you have used to test the bpel service.
Are you testing in EM console itself?? or you are using SOAP UI tool to test it??
If you are using SOAP UI tool check properly the request has been reached to the service or not. sometimes it throws an error if request is not proper.
If ypu are using EM console to test it, give the proper input fields and click on Test web service button. after that go to soa_infra and click on the servce which you are testing so that page will get refresed and able to see the instance.