Validation rule is not working though formatting rule with the exact condition is working.

[kurodak]

I made a formatting rule as below and it is working properly.

and(Status=="Final Report",{Self}=="")

However it is not woking if it is changed to validation rule.

[sojanm]

Try 

Status=="Final Report" && {Self} ==""

[kurodak]

I've changed it as suggested but it is not woking.

Status=="Final Report" && {Self} ==""

[sojanm]

What are the controls for status and self

[kurodak]

The status is the choice control and self is the date control.

However it is resolved by deleting the form and creating a new one.