Hi Gobi,
Your first error might be the common error faced by many before. Please grant access to _SYS_REPO user to the schema which contains the tables on which you are trying to create the attribute view:
GRANT SELECT ON SCHEMA <schema_name> TO _SYS_REPO WITH GRANT OPTION;
You can also do that graphically with opening the _SYS_REPO user in security and adding the schema containing tables and assign the SELECT access with grant to others option.
Your second issue might be related to first one, hence please try to resolve the first issue and post again.
Regards,
Ravi