Can not find the AC Owner by owner name

Hello,

While assigning mitigation owners to mitigation controls in GRC AC10.0., system is not displaying the owners (no results found), though we have configured user ids as Risk, Mitigation owners through Access Control Owners.

Adding owners in manually is also giving the  error ' Can not find the AC Owner by owner name sumanth '

Can anyone help me here pls?

Regards,

Sumanth