Closing alert should resolve incident automatically

[Kumar54]

In event management settings closing alerts was set to resolve incidents automatically but i see no incidents getting resolved though the alert is closed?

[VaranAwesomenow]

The name of BR is

Close associated incident | Business Rule | ServiceNow (service-now.com)

existing condition : 

((previous.state != 'Closed' && current.state == 'Closed')||(previous.severity != '5' && current.severity == '5') ||(previous.severity != '0' && current.severity == '0')) && current.incident !='NULL' && current.incident !='' && current.incident !=null

which translates to

      If Alert gets closed or

       if Alert severity changes to either OK or Clear

      AND

incident is not empty.