Best Practice for Calling AP_VENDOR_PUB_PKG.create_vendor API

We are trying to build an interface between Banner and Oracle EBS (R12.2.10) to create/update Student vendors. We have a custom PL/SQL package that is calling the AP_VENDOR_PUB_PKG.create_vendor API. There is an external application that calls the custom PL/SQL package, so it is not run via concurrent manager. The problem we have is that when the it is executed this way the API call to create_vendor is failing with table or view not found. We've tried changing the AUTHID from Current User to Definer in the custom package, but that didn't work. We tried running as