TypeError: response.data is undefined - vue.js

Question

I'm having problems with promise response for a vForm PUT to UPDATE a model (backend in laravel).
The response code is 200 (OK, updated) and the model is updated, but I don't know why I'm having error with "response.data" in catch. There is no error and code in ".then()" is running correctly.
EDIT
Service Update funciton (vue) using vForm.
updateService(){
this.$Progress.start();
this.service.put('api/service/' + this.service.id)
.then( function (response) {
Toast.fire({
type: 'success',
title: response.data['Response']
});
this.$Progress.finish();
})
.catch( function (response) {
console.log(response);
Swal.fire("Error!", response.data['Response'], "warning");
this.$Progress.fail();
});
this.$events.$emit('ServiceInform');
},
Function in backend (laravel).
public function update(Request $request, Service $service)
{
$this->validate($request, [
'id_customers' => 'required|int',
'date' => 'required|date',
'id_technicians' => 'required|int',
'location' => 'required|string',
'details' => 'required|string'
]);
if ($request['id_technicians'] !== $service['id_technicians']) {
$assignated_by = Auth::user()->id;
$assigned_date = date('Y-m-d H:i:s');
} else {
$assignated_by = $service['assignated_by'];
$assigned_date = $service['assigned_date'];
}
if ($request['id_technicians'] == 0) {
$state = 'P';
} else {
$state = 'I';
}
$service->date = $request['date'];
$service->id_technicians = $request['id_technicians'];
$service->location = $request['location'];
$service->details = $request['details'];
$service->assigned_date = $assigned_date;
$service->assigned_by = $assignated_by;
$service->state = $state;
try {
$service->save();
return Response::json([
'Response' => 'Servicio actualizado.'
], 201);
} catch (Exception $e) {
return Response::json([
'Response' => 'No se actualizó el servicio.'
], 422);
}
}

Answer 1

This line looks problematic to me:
this.$Progress.finish();
It's trying to access this within the function passed to then. It seems unlikely that this will be referencing what you're expecting. You should be able to confirm with suitable console logging. My suspicion is that attempting to call this.$Progress.finish() will throw an error, triggering the catch.
Try using arrow functions for your then and catch callbacks instead.