It appears like you are looking for 'Authorization Dependency Viewer'.
It is graphical tool and might be helpful to pinpoint the exact privilege that the end user might be missing.
Step #1
Use Authorization Dependency Viewer to see where exactly it is failing
(note this requires system privilege CATALOG READ or DATA ADMIN.)
(for more details search Resolve Errors Using the Authorization Dependency Viewer in Admin guide)
Step # 2
I would start with reviewing Roles / Object privileges at high level for that specific user.
The method I approach is first list out the roles / privs that user needs to access your objects..i know that's what you are trying to figure out but having list of roles / privs that user MUST have comes handy..and then deep dive..else the dependency viewer might be confusing sometimes..
some queries below that might be of help
--All privileges granted to the specified user both directly and indirectly through roles are listed separately.
SELECT * FROM "PUBLIC"."EFFECTIVE_PRIVILEGES" where USER_NAME = 'Enter User Name Here';
--All roles granted to the specified user both directly and indirectly through other roles are listed separately.
SELECT * FROM "PUBLIC"."EFFECTIVE_ROLES" where USER_NAME = 'Enter User Name Here'
--All application privileges granted to the specified user both directly and indirectly through roles are listed separately.
select * from "SYS"."EFFECTIVE_APPLICATION_PRIVILEGES" where USER_NAME='Enter User Name Here';
--All views that the user is authorized to access are listed.
SELECT * from "PUBLIC"."ACCESSIBLE_VIEWS" where USER_NAME = 'Enter User Name Here';
Please let us know how it goes..good luck