Try to connect rman with external authenticated user. Insufficient privilege

 Dear expert,

              I have a problem while connecting to RMAN. The problem is as the following senario.

              I have one external authenticated user account(Window authenticate user name XXX, oracle account OPS$XXX), this OS account was use to check the application process(non-oracle operations). If success it will backup oracle by hot-backup with old solution (Take tablespace backup and use ocopy). But now I want to use RMAN as one choice to backup. So I try to connect to RMAN with this account. It return error "insufficient privilege"

              I've granted "sysdba, sysoper" even "dba" to OPS$XXX. But no effect, it has the same errors. I figured that the problem is from when I connect I try to connect as the following.