Materialized view not refreshing automatically after import

 Hi,

Materialized views are not refreshing automatically after import.

Giving error in alert log

ORA-12012: error on auto execute of job 515
ORA-01031: insufficient privileges
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2251
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2457
ORA-06512: at "SYS.DBMS_IREFRESH", line 685
ORA-06512: at "SYS.DBMS_REFRESH", line 195
ORA-06512: at line 1

I have already given

grant execute on DBMS_SNAPSHOT to user

grant execute on DBMS_IREFRESH  to user

grant execute on DBMS_REFRESH to user

Please suggest.

BR///

nk

PS: The export and import was done by system user.