Granting select to table------------giving error

Hello,
I logged in sys "/as sysdba"

and granting privileges to other users like   >>grant select on <schema_name>.<table_name> to <username>;
but its giving error like

ERROR at line 1:
ORA-01031: insufficient privileges

Im having all sysdba privileges
GRANTEE                        GRANTED_ROLE                   ADM
------------------------------ ------------------------------ ---
SYS                            ALL_OBJECTS                             YES
SYS                            AQ_ADMINISTRATOR_ROLE          YES
SYS                            AQ_USER_ROLE                        YES
SYS                            CONNECT                                  YES
SYS                            CUSTOM_PUBLIC                         YES
SYS                            DBA                                            YES
SYS                            DELETE_CATALOG_ROLE            YES
SYS                            EXECUTE_CATALOG_ROLE           YES
SYS                            EXP_FULL_DATABASE                     YES
SYS                            GMRADMIN                                      YES
SYS                            HS_ADMIN_ROLE                            YES
SYS                            IMP_FULL_DATABASE                     YES
SYS                            JAVADEBUGPRIV                            YES