ajax/getJSON call fails with no error... help!

ajax/getJSON call fails with no error... help!

Hi
I am trying to amend some legacy jquery code written by someone else - I'm not a jquery expert... :-(

I have a call to getJSON that for some reason started to fail and I couldn't see why. I rewrote it to use $.ajax so I could see what was going on. I have added an error and complete function and also  .done, always & .fail to try and see what is happening but neither these nor the original success function are being called.

I have spent 3 days now trying to figurre out what is going wrong and I am at my wits end...

Does anyone have any ideas what might be going wrong or what I can try?

I am using jquery-3.3.1. I am watching the code with breakpoints right up to this point and all the variables have appropriate values (and this code used to work). The code that is causing problems looks like this (none of the debugging alerts is triggered and the page just seems to reload):

  $.ajax({
data: accountValidation,
    cache: false,
type: 'GET',
dataType: 'json',
complete: function (jqXHR, status) {
   alert("PCA bank check completed..."+status);
  },
    error:function (xhRequest, errorText, thrownError) { 
        alert("PCA bank check not working - Error:"+errorText); 
    } ,
success: function (data) {
alert("Checking PCA Bank details... status info="+data.Items[0].StatusInformation);
                              // functionality code goes here but has been removed for simplicity...

}
  })
  .done(function (data, status, jqXHR) {
  $("#container").html(data);
  alert("successful PCA bank validation callback.");
  })
  .fail(function (jqXHR,status,err) {
  alert("error communicating with pca bank validation - error:"+err);
  }).always(function () {
    alert("Completed PCA bank callback.");  
  });

...help!