Fixed

// constants won't change. They're used here to set pin numbers:
const int Ls = 4;     // the number of the lock pin
const int Lock = 21;      // the number of the Locked relay
const int Us = 5;     // the number of the unlock pin
const int Lights = 17;      // the number of the Lights relay

// variables will change:
int LsState = 0;         // variable for reading the Lock status
int UsState = 0;         // variable for reading the Unlock status

void setup() {
  pinMode(Lock, OUTPUT);  // initialize Lock as an output:
  pinMode(Ls, INPUT); // initialize the Ls pushbutton as an input:
  pinMode(Lights, OUTPUT); // initialize the Lights pin as an output:
  pinMode(Us, INPUT);  // initialize the Us pin as an input:
}

void loop() {
  // read the state of the Lock value:
  LsState = digitalRead(Ls);   // check if the pushbutton is pressed. If it is, the LsState is HIGH:
  if (LsState == HIGH) {      // turn Lock output on:
    digitalWrite(Lock, HIGH);
    digitalWrite(Lights, LOW);
    }

  // read the state of the Unlock value:
  UsState = digitalRead(Us);   // check if the pushbutton is pressed. If it is, the UsState is HIGH:
  if (UsState == HIGH) {      // turn Lights relay on:
    digitalWrite(Lights, HIGH);
    digitalWrite(Lock, LOW);
    }

  }