How does send email on update rule works

Summary

How does send email on update rule works

Content

Hi All,

We are trying to achieve one requirement where if for any reconciliation there is an unexplained difference then system should trigger mail to reviewer 1.

We are leveraging this send email on update rule for the same where we have specified condition and selected reviewer 1 check box. But its not working.

Any idea on how to achieve the same?

Regards,

Dishil