If a bpel fails to create any instance you can take a look at the "View Process Log", its a worth try.

Click on this link "View Process Log" to get the failed bpel information.

In one of my project i was working with AQ, when we try to move the code from DEV to TEST, we were hit with this issue.
We have every thing in place, we have created AQ and we have created the required DataSource and when we push message to the AQ.
The BPEL is not picking up the AQ Message, we checked each and every thing that we could.

We looked at all the logs from the server and we couldnt identify the issue. Then i clicked on the view process log. We got the below exception.

"ORA-06550: line 1, column 7: PLS-00201: identifier 'DBMS_AQIN' must be declared ORA-06550: line 1, column 7: PL/SQL: Statement ignored"

Basically we dont have the permission to dequeue, because of the above permission is not there for that user. Once we granted for this user. we were able to
goahead with our testing.