Chgrp is not working

whenever I try to change the group of a file I always get this error.


chgrp: changing group of `file_dir’: Operation not permitted

Does something else need to be configured on the account?

It looks like you don’t own the group you are trying to change to

I created all the groups myself.
How do you get to own a group using the master acccount if you don’t own it? How do you tell which account owns a group?

I may have created a few groups using a different account.