Please can you share the verison of software.
X A H E E R
Is this from a standalone sql session? You need to initialize your session. Try at least:
mo_global.init( 'AR' ) ;
And just in case also use fnd_global.apps_initialize
I have done APPS INITIALIZE just before calling the API.
FND_GLOBAL.APPS_INITIALIZE (USER_ID => crec.target_user_id, RESP_ID => crec.responsibility_id, RESP_APPL_ID => 222) ;
Created a Procedure and calling that from a workflow package.