Need Input: Wait for voltage input to begin script & when voltage maintains 0V for X amount of time Reset and wait for Voltage Input
It's hard to know where to start here. :)



 if (currentMillis + 500)


OK, what is that doing? It is adding 500 to currentMillis so that will be true almost all the time.



if (status = 3)


That is assigning 3 to status and then checking if it is non-zero, which it will be (it will be 3).



int turnPin = A1;
...

  int sensorValue = analogRead(A1);


Why not write:

  int sensorValue = analogRead(turnPin);




float voltage = sensorValue * (5.0 / 1023.0);


You calculate voltage but never use it. Why bother?




  As for your question regarding if (currentMillis + 500) I wanted this statement to take the current time and add 500 to it and then check ...


OK, then this is the way to do that:

// see if 1/2 a second is up
if (currentMillis - previousMillis &gt;= 500)
   {
   previousMillis = currentMillis;  // reset previousMillis
   ... do something ...
   }


BTW, previousMillis is also a variable you weren't using anywhere else.