I want to compare 2 dates and make if else

In Google Sheet I want to compare two dates and check if either one (Plan start date ,Actual start date) is blank, show text as "not started " if not if (plan start date

=if((DAYS360(D8,C8)<0,"Delay","Inline",IF(ISBLANK(D8),"Not started")))

This didn't work. Can anyone help?