from the looks of things, you're not  really using "OR" at all.
Let's say you have:
AE2 = 1
AF2 = 4000
AN2 = 50
then your "AND(AE2< =1,AF2<=4000, AN2<75)" results  in True,
so returns "Candidate".

But if, say, AE2 = 2
then your "AND" returns FALSE, so then evaluates:
IF((OR(AD2= "dead", AD2," Not Candidate")) )
but if you look closely, the "OR" construct is incomplete.
"OR" should be like: "OR(expression,expression,expression,...)
each expression testing for true/false, but yours is testing the
CONTENTS of AD2 and the string "Not Candidate"..
from what I see, you're really simply using a nested if.

Try this:
=IF(AND(AE2<=1,AF2<=4000,AN2<75)," Candidate",
IF(AD2="dead",AD2," Not Candidate"))
(watch the wrap-around)