Laravel 8 [Yajra DataTable] - DataTables warning: table id=userTable - Invalid JSON response - php

Question

I am trying to display all User (Where status is = 1) Data from database into DataTable using Yajra Package in Laravel but it always displays this error:
DataTables warning: table id=userTrashBin - Invalid JSON response. For more information about this error, please see http://datatables.net/tn/1
When I check the response (In Developer's tools > Network Tab) it does not have any or it show Failed to load response data:
Here's my datatable() inside the UserController.php:
public function datatable()
{
$data = User::where('status', '=', 1)->get();
return DataTables::of($data)
->addColumn('action', function($data){
$url_edit = url('user/'.$data->id.'/edit');
$url_deact = url('user/deactivateUser/'.$data->id);
$url = url('user/'.$data->id);
$view = "<a class = 'btn btn-primary' href = '".$url."' title = 'View'><i class = 'nav icon fas fa-eye'></i></a>";
$edit = "<a class = 'btn btn-warning' href = '".$url_edit."' title = 'Edit'><i class = 'nav icon fas fa-edit'></i></a>";
$delete = "<button data-url = '".$url_deact."' onclick = 'deleteData(this)' class = 'btn btn-action btn-danger' title = 'Deactivate'><i class = 'nav-icon fas fa-trash-alt'></i></button>";
return $view."".$edit."".$delete;
})->editColumn('user_type', function($data){
$dataUser = User::find($data->id)->first();
$returnStr = "";
if($dataUser->hasRole('A')){
$returnStr = "Administrator";
}else{
$returnStr = "Employee";
}
return $returnStr;
})
->rawColumns(['action'])
->make(true);
}
Here's the script file in index.blade.php:
$("#userTable").DataTable({
responsive:true,
processing:true,
pagingType: 'full_numbers',
stateSave:false,
scrollY:true,
scrollX:true,
autoWidth: false,
ajax:"{{ url('user/datatable') }}",
columns:[
{data:'first_name', name: 'first_name'},
{data:'last_name', name: 'last_name'},
{data:'email', name: 'email'},
{data:'user_type', name: 'user_type'},
{data:'action', name: 'action', searchable: true, sortable:true},
]
});
The route for user/datatable inside web.php:
Route::get('user/datatable', 'UserController#datatable')->name('user/datatable')->middleware('role:A');
And finally the index.blade.php file where the userTable is located:
<table id="userTable" class="table table-bordered table-striped" data-toggle = "table1_" style = "width: 100%;">
<thead>
<tr>
<th>First Name</th>
<th>Last Name</th>
<th>E-Mail Address</th>
<th>User Type</th>
<th>Action</th>
</tr>
</thead>
<tfoot>
<tr>
<th>First Name</th>
<th>Last Name</th>
<th>E-Mail Address</th>
<th>User Type</th>
<th>Action</th>
</tr>
</tfoot>
</table>
I don't know what causes the error and how to fix it for now because it doesn't have any response data or other error/s that will give me a hint.