Whenever I try to pull data from 2 of 3 sheets from using the 'google.script.run' function call from Javascript, I keep getting an error saying the array I am returning is Null, but when I just change the exact same function call to work on another sheet, it returns the data perfectly 

I have tried deleting the sheets and giving it the same names, I have tried using 'openWithURL' instead of 'getActive' to access the spreadsheet, I have tried rewriting the code, I have tried the same code in a different project, and checking the documentation to make sure I am not missing any detail. I have tried changing the references to the sheets, some work and some dont.

```
var SS = SpreadsheetApp.getActive();

var DB_BOOKINGS = SS.getSheetByName("BookingDatabase");
var DB_VEHICLES = SS.getSheetByName("VehicleDatabase");
var DB_REQUESTS = SS.getSheetByName("RequestDatabase");

function getRequestData(){

 return DB_REQUESTS.getDataRange().getValues(); 
}

<script>
      function getRequestData(callingFunction) {
         google.script.run
         .withSuccessHandler(callingFunction)
         .withFailureHandler(CustomAlert)
         .getRequestData();

        }
</script>

```

I want to retrieve the sheet data but keep getting a null value