I am sorry, but Sara is unable to determine your SendOnBehalfOf permission issue. Delegate {1} does have proper permissions ...

I am sorry, but Sara is unable to determine your SendOnBehalfOf permission issue.  Delegate {1} does have proper permissions for Principal {0}. Please note that recent changes in delegate permissions can take up to two hours to be reflected. If it has been longer, please try removing all delegate permissions via the principal mailbox and recreate the permission. Otherwise, please file a support ticket with your administrator and someone will be able to help you personally with your issue.